Miscellany

Jai Ganesh · 2025-01-04 00:02:19

2301) Thermal Printing

Gist

Thermal printing (or direct thermal printing) is a digital printing process which produces a printed image by passing paper with a thermochromic coating, commonly known as thermal paper, over a print head consisting of tiny electrically heated elements.

Summary

Thermal printing is a technique in which an image is printed on thermal paper by means of heat.

The heat is applied by a controlled printhead. The thermal paper, on the other hand, has a heat-sensitive coating that allows the heat to produce the marking.

Types of thermal printing

There are two types of thermal printing methods: direct thermal printing and thermal transfer printing.

In the case of direct thermal printing, the heat from the printhead is applied directly to the thermal paper. This causes a chemical reaction in the special heat-sensitive layer of the laminate material, turning the paper black. It is worth being noted that modern thermal paper is much more resistant to environmental influences than before so that the colour stays fresh for several years.

Thermal transfer printing, on the other hand, uses colour foil, or thermal transfer foil, to get the print on the paper. The printhead is equipped with hundreds of tiny heating elements that can be computer-control activated. The foil runs between the printhead and paper and is melted by the printhead where the heating elements are activated. The plain surface of the foil achieves a fine and sharp print with a slight shine. The advantage of the thermal-transfer system is the longer shelf life of its prints compared to the direct-thermal prints.

Thermal printing and inkjet printing systems

Thermal printers that have to print directly on the product packaging often use inkjet printing systems. The main advantage is that these systems are able to print on various surfaces like paper, cardboard packaging, synthetic materials or metal. Inkjet printing is especially used for pharmaceutical, cosmetic and food packaging, as well as in the postal service.

Thermal printers powered with inkjet printing systems use ink cartridges with lots of tiny chambers that can be heated by an electric impulse. The heat provokes the building of a small vapour bubble which pushes the ink through the nozzle. The tension of the vapour bubble, as well as the surface tension of the ink drop, cause the ink to hurl back within a fraction of a second. Precise and high quality prints of text, barcodes and graphics can therefore be achieved.

Another combination of thermal printing with inkjet printing technology is the so-called piezoelectric inkjet printing process, or piezo inkjet printing. In this case, the walls of the ink chamber are heated by an electrical pulse, so that they extend through the heat. The ink is pressed out of the nozzle and onto the object. By stopping the electric impulse, the walls return to their original position. In the chamber a vacuum is created, pulling the rest of the ink that has not been used for the print back into the cartridge.

Details

Thermal printing (or direct thermal printing) is a digital printing process which produces a printed image by passing paper with a thermochromic coating, commonly known as thermal paper, over a print head consisting of tiny electrically heated elements. The coating turns black in the areas where it is heated, producing an image.

Most thermal printers are monochrome (black and white) although some two-color designs exist.

Thermal-transfer printing is a different method, using plain paper with a heat-sensitive ribbon instead of heat-sensitive paper, but using similar print heads.

Design

A thermal printer typically contains at least these components:

* Thermal head: Produces heat to create an image on the paper
* Platen: A rubber roller which moves the paper
* Spring: Applies pressure to hold the paper and printhead together

Thermal paper is impregnated with a solid-state mixture of a dye and a suitable matrix, for example, a fluoran leuco dye and an octadecylphosphonic acid. When the matrix is heated above its melting point, the dye reacts with the acid, shifts to its colored form, and the changed form is then conserved in metastable state when the matrix solidifies back quickly enough, a process known as thermochromism.

This process is usually monochrome, but some two-color designs exist, which can print both black and an additional color (often red) by applying heat at two different temperatures.

In order to print, the thermal paper is inserted between the thermal head and the platen and pressed against the head. The printer sends an electric current to the heating elements of the thermal head. The heat generated activates the paper's thermochromic layer, causing it to turn a certain color (for example, black).

Thermal print heads can have a resolution of up to 1,200 dots per inch (dpi). The heating elements are usually arranged as a line of small closely spaced dots.

Early formulations of the thermo-sensitive coating used in thermal paper were sensitive to incidental heat, abrasion, friction (which can cause heat, thus darkening the paper), light (which can fade printed images), and water. Later thermal coating formulations are far more stable; in practice, thermally printed text should remain legible for at least 50 days.

Applications

Thermal printers print more quietly and usually faster than impact dot matrix printers. They are also smaller, lighter and consume less power, making them ideal for portable and retail applications.

Commercial use

Commercial applications of thermal printers include filling station pumps, information kiosks, point of sale systems, voucher printers in slot machines, print on demand labels for shipping and products, and for recording live rhythm strips on hospital cardiac monitors.

Record-keeping in microcomputers

Many popular microcomputer systems from the late 1970s and early 1980s had first-party and aftermarket thermal printers available for them, such as the Atari 822 printer for the Atari 8-bit computers, the Apple Silentype for the Apple II, and the Alphacom 32 for the ZX Spectrum and ZX81. They often use unusually-sized supplies (10CM wide rolls for the Alphacom 32 for instance) and were often used for making permanent records of information in the computer (graphics, program listings etc.), rather than for correspondence.

Fax machines

A fax machine from Panasonic with integrated answering machine, beginning of the 1990s. The thermal paper was sold in rolls which were inserted into a compartment in the device. After a completed transmission, the printed document was automatically cut off from the roll and remained in front of the machine.

Through the 1990s, many fax machines used thermal printing technology. Toward the beginning of the 21st century, however, thermal wax transfer, laser, and inkjet printing technology largely supplanted thermal printing technology in fax machines, allowing printing on plain paper.

Seafloor Exploration

Thermal printers are commonly used in seafloor exploration and engineering geology due to their portability, speed, and ability to create continuous reels or sheets. Typically, thermal printers found in offshore applications are used to print realtime records of side scan sonar and sub-seafloor seismic imagery. In data processing, thermal printers are sometimes used to quickly create hard copies of continuous seismic or hydrographic records stored in digital SEG Y or XTF form.

Other uses

Flight progress strips used in air traffic control (ACARS) typically use thermal printing technology.

In many hospitals in the United Kingdom, many common ultrasound sonogram devices output the results of the scan onto thermal paper. This can cause problems if the parents wish to preserve the image by laminating it, as the heat of most laminators will darken the entire page—this can be tested beforehand on an unimportant thermal print. An option is to make and laminate a permanent ink duplicate of the image.

The Game Boy Printer, released in 1998, was a small thermal printer used to print out certain elements from some Game Boy games.

Health concerns

Reports began surfacing of studies in the 2000s finding the oestrogen-related chemical bisphenol A ("BPA") mixed in with thermal (and some other) papers. While the health concerns are very uncertain[citation needed], various health and science oriented political pressure organizations, such as the Environmental Working Group, have pressed for these versions to be pulled from market.

Additional Information

Thermal printers are dot-matrix printers that operate by driving heated pins against special heat-sensitive paper to “burn” the image onto the paper. They are quiet, but many people don't like the feel of thermal paper, and the images tend to fade.

Thermal printers are favored for their simplicity, speed, and reliability. They're used extensively in industries like retail, healthcare, logistics, and manufacturing for their cost-effectiveness and ability to generate high-resolution prints very quickly.

Thermal printers are dot-matrix printers that operate by driving heated pins against special heat-sensitive paper to “burn” the image onto the paper. They are quiet, but many people don't like the feel of thermal paper, and the images tend to fade.

Jai Ganesh · 2025-01-04 21:04:03

2302) Scientist

Gist

A scientist is someone who systematically gathers and uses research and evidence, to make hypotheses and test them, to gain and share understanding and knowledge. A scientist can be further defined by: how they go about this, for instance by use of statistics (statisticians) or data (data scientists).

Summary

A scientist is a person who studies or has mastered the field in science. A scientist tries to understand how our world, or other things, work. Scientists make observations, ask questions and do extensive research work in finding the answers to many questions.

Scientists may work in laboratories for governments, companies, schools and research institutions. Some scientists teach at universities and other places and train people to become scientists. Scientists often do experiments to find out more about reality, and sometimes may repeat experiments or use control groups. Scientists who are doing applied science try to use scientific knowledge to improve the world.

Scientists use the Scientific method to test theories and hypotheses.

Details

A scientist is a person who researches to advance knowledge in an area of the natural sciences.

In classical antiquity, there was no real ancient analog of a modern scientist. Instead, philosophers engaged in the philosophical study of nature called natural philosophy, a precursor of natural science. Though Thales (c. 624–545 BC) was arguably the first scientist for describing how cosmic events may be seen as natural, not necessarily caused by gods, it was not until the 19th century that the term scientist came into regular use after it was coined by the theologian, philosopher, and historian of science William Whewell in 1833.

History

"No one in the history of civilization has shaped our understanding of science and natural philosophy more than the great Greek philosopher and scientist Aristotle (384-322 BC), who exerted a profound and pervasive influence for more than two thousand years" —Gary B. Ferngren

Georgius Agricola gave chemistry its modern name. Generally referred to as the father of mineralogy and the founder of geology as a scientific discipline.

Johannes Kepler, one of the founders and fathers of modern astronomy, the scientific method, natural and modern science.

Alessandro Volta, the inventor of the electrical battery and discoverer of methane, is widely regarded as one of the greatest scientists in history.

Francesco Redi, referred to as the "father of modern parasitology", is the founder of experimental biology.

Isaac Newton, who is regarded as "the towering figure of the Scientific Revolution", and who achieved the first great unification in physics, created classical mechanics, calculus and refined the scientific method.

Mary Somerville, for whom the word "scientist" was coined.

Physicist Albert Einstein developed the general theory of relativity and made many substantial contributions to physics.

Physicist Enrico Fermi is credited with the creation of the world's first atomic bomb and nuclear reactor.

Atomic physicist Niels Bohr made fundamental contributions to understanding atomic structure and quantum theory.

Marine Biologist Rachel Carson launched the 20th century environmental movement.

The roles of "scientists", and their predecessors before the emergence of modern scientific disciplines, have evolved considerably over time. Scientists of different eras (and before them, natural philosophers, mathematicians, natural historians, natural theologians, engineers, and others who contributed to the development of science) have had widely different places in society, and the social norms, ethical values, and epistemic virtues associated with scientists—and expected of them—have changed over time as well. Accordingly, many different historical figures can be identified as early scientists, depending on which characteristics of modern science are taken to be essential.

Some historians point to the Scientific Revolution that began in 16th century as the period when science in a recognizably modern form developed. It was not until the 19th century that sufficient socioeconomic changes had occurred for scientists to emerge as a major profession.

Classical antiquity

Knowledge about nature in classical antiquity was pursued by many kinds of scholars. Greek contributions to science—including works of geometry and mathematical astronomy, early accounts of biological processes and catalogs of plants and animals, and theories of knowledge and learning—were produced by philosophers and physicians, as well as practitioners of various trades. These roles, and their associations with scientific knowledge, spread with the Roman Empire and, with the spread of Christianity, became closely linked to religious institutions in most European countries. Astrology and astronomy became an important area of knowledge, and the role of astronomer/astrologer developed with the support of political and religious patronage. By the time of the medieval university system, knowledge was divided into the trivium—philosophy, including natural philosophy—and the quadrivium—mathematics, including astronomy. Hence, the medieval analogs of scientists were often either philosophers or mathematicians. Knowledge of plants and animals was broadly the province of physicians.

Middle Ages

Science in medieval Islam generated some new modes of developing natural knowledge, although still within the bounds of existing social roles such as philosopher and mathematician. Many proto-scientists from the Islamic Golden Age are considered polymaths, in part because of the lack of anything corresponding to modern scientific disciplines. Many of these early polymaths were also religious priests and theologians: for example, Alhazen and al-Biruni were mutakallimiin; the physician Avicenna was a hafiz; the physician Ibn al-Nafis was a hafiz, muhaddith and ulema; the botanist Otto Brunfels was a theologian and historian of Protestantism; the astronomer and physician Nicolaus Copernicus was a priest. During the Italian Renaissance scientists like Leonardo da Vinci, Michelangelo, Galileo Galilei and Gerolamo Cardano have been considered the most recognizable polymaths.

Renaissance

During the Renaissance, Italians made substantial contributions in science. Leonardo da Vinci made significant discoveries in paleontology and anatomy. The Father of modern Science, Galileo Galilei, made key improvements on the thermometer and telescope which allowed him to observe and clearly describe the solar system. Descartes was not only a pioneer of analytic geometry but formulated a theory of mechanics and advanced ideas about the origins of animal movement and perception. Vision interested the physicists Young and Helmholtz, who also studied optics, hearing and music. Newton extended Descartes's mathematics by inventing calculus (at the same time as Leibniz). He provided a comprehensive formulation of classical mechanics and investigated light and optics. Fourier founded a new branch of mathematics — infinite, periodic series — studied heat flow and infrared radiation, and discovered the greenhouse effect. Girolamo Cardano, Blaise Pascal Pierre de Fermat, Von Neumann, Turing, Khinchin, Markov and Wiener, all mathematicians, made major contributions to science and probability theory, including the ideas behind computers, and some of the foundations of statistical mechanics and quantum mechanics. Many mathematically inclined scientists, including Galileo, were also musicians.

There are many compelling stories in medicine and biology, such as the development of ideas about the circulation of blood from Galen to Harvey. Some scholars and historians attributes Christianity to having contributed to the rise of the Scientific Revolution.

Age of Enlightenment

During the age of Enlightenment, Luigi Galvani, the pioneer of bioelectromagnetics, discovered animal electricity. He discovered that a charge applied to the spinal cord of a frog could generate muscular spasms throughout its body. Charges could make frog legs jump even if the legs were no longer attached to a frog. While cutting a frog leg, Galvani's steel scalpel touched a brass hook that was holding the leg in place. The leg twitched. Further experiments confirmed this effect, and Galvani was convinced that he was seeing the effects of what he called animal electricity, the life force within the muscles of the frog. At the University of Pavia, Galvani's colleague Alessandro Volta was able to reproduce the results, but was sceptical of Galvani's explanation.

Lazzaro Spallanzani is one of the most influential figures in experimental physiology and the natural sciences. His investigations have exerted a lasting influence on the medical sciences. He made important contributions to the experimental study of bodily functions and animal reproduction.

Francesco Redi discovered that microorganisms can cause disease.

19th century

Until the late 19th or early 20th century, scientists were still referred to as "natural philosophers" or "men of science".

English philosopher and historian of science William Whewell coined the term scientist in 1833, and it first appeared in print in Whewell's anonymous 1834 review of Mary Somerville's On the Connexion of the Physical Sciences published in the Quarterly Review. Whewell wrote of "an increasing proclivity of separation and dismemberment" in the sciences; while highly specific terms proliferated—chemist, mathematician, naturalist—the broad term "philosopher" was no longer satisfactory to group together those who pursued science, without the caveats of "natural" or "experimental" philosopher. Whewell compared these increasing divisions with Somerville's aim of "[rendering] a most important service to science" "by showing how detached branches have, in the history of science, united by the discovery of general principles." Whewell reported in his review that members of the British Association for the Advancement of Science had been complaining at recent meetings about the lack of a good term for "students of the knowledge of the material world collectively." Alluding to himself, he noted that "some ingenious gentleman proposed that, by analogy with artist, they might form [the word] scientist, and added that there could be no scruple in making free with this term since we already have such words as economist, and atheist—but this was not generally palatable".

Whewell proposed the word again more seriously (and not anonymously) in his 1840 The Philosophy of the Inductive Sciences:

The terminations ize (rather than ise), ism, and ist, are applied to words of all origins: thus we have to pulverize, to colonize, Witticism, Heathenism, Journalist, Tobacconist. Hence we may make such words when they are wanted. As we cannot use physician for a cultivator of physics, I have called him a Physicist. We need very much a name to describe a cultivator of science in general. I should incline to call him a Scientist. Thus we might say, that as an Artist is a Musician, Painter, or Poet, a Scientist is a Mathematician, Physicist, or Naturalist.

He also proposed the term physicist at the same time, as a counterpart to the French word physicien. Neither term gained wide acceptance until decades later; scientist became a common term in the late 19th century in the United States and around the turn of the 20th century in Great Britain. By the twentieth century, the modern notion of science as a special brand of information about the world, practiced by a distinct group and pursued through a unique method, was essentially in place.

20th century

Marie Curie became the first woman to win the Nobel Prize and the first person to win it twice. Her efforts led to the development of nuclear energy and Radiotherapy for the treatment of cancer. In 1922, she was appointed a member of the International Commission on Intellectual Co-operation by the Council of the League of Nations. She campaigned for scientist's right to patent their discoveries and inventions. She also campaigned for free access to international scientific literature and for internationally recognized scientific symbols.

Profession

As a profession, the scientist of today is widely recognized. However, there is no formal process to determine who is a scientist and who is not a scientist. Anyone can be a scientist in some sense. Some professions have legal requirements for their practice (e.g. licensure) and some scientists are independent scientists meaning that they practice science on their own, but to practice science there are no known licensure requirements.

Education

In modern times, many professional scientists are trained in an academic setting (e.g., universities and research institutes), mostly at the level of graduate schools. Upon completion, they would normally attain an academic degree, with the highest degree being a doctorate such as a Doctor of Philosophy (PhD). Although graduate education for scientists varies among institutions and countries, some common training requirements include specializing in an area of interest, publishing research findings in peer-reviewed scientific journals and presenting them at scientific conferences, giving lectures or teaching,[44] and defending a thesis (or dissertation) during an oral examination. To aid them in this endeavor, graduate students often work under the guidance of a mentor, usually a senior scientist, which may continue after the completion of their doctorates whereby they work as postdoctoral researchers.

Career

After the completion of their training, many scientists pursue careers in a variety of work settings and conditions. In 2017, the British scientific journal Nature published the results of a large-scale survey of more than 5,700 doctoral students worldwide, asking them which sectors of the economy they would like to work in. A little over half of the respondents wanted to pursue a career in academia, with smaller proportions hoping to work in industry, government, and nonprofit environments.

Other motivations are recognition by their peers and prestige. The Nobel Prize, a widely regarded prestigious award, is awarded annually to those who have achieved scientific advances in the fields of medicine, physics, and chemistry.

Some scientists have a desire to apply scientific knowledge for the benefit of people's health, the nations, the world, nature, or industries (academic scientist and industrial scientist). Scientists tend to be less motivated by direct financial reward for their work than other careers. As a result, scientific researchers often accept lower average salaries when compared with many other professions which require a similar amount of training and qualification.

Research interests

Scientists include experimentalists who mainly perform experiments to test hypotheses, and theoreticians who mainly develop models to explain existing data and predict new results. There is a continuum between the two activities and the division between them is not clear-cut, with many scientists performing both tasks.

Those considering science as a career often look to the frontiers. These include cosmology and biology, especially molecular biology and the human genome project. Other areas of active research include the exploration of matter at the scale of elementary particles as described by high-energy physics, and materials science, which seeks to discover and design new materials. Others choose to study brain function and neurotransmitters, which is considered by many to be the "final frontier". There are many important discoveries to make regarding the nature of the mind and human thought, much of which still remains unknown.

Additional Information:

Introduction

Through the ages, people have sought to better understand how and why things happen in the universe. Scientists developed an approach to keep track of what was learned and to make sure it was true. Findings were tested and recorded so that others could use those ideas to solve new problems. Over time, scientific discoveries have changed the way people live and think.

The dates given for the scientists in this section are for their most notable scientific achievement or for the time period when they were most active in their scientific studies.

Ancient Times

Plato (387 bce)
Aristotle (300s bce)
Euclid (300s–200s bce)
Aristarchus of Samos (200s bce)
Archimedes (200s bce)
Ptolemy (100s ce)
Hypatia (late 300s)
al-Khwarizmi (800s)

1400s Through 1700s

Leonardo da Vinci (1490s–1510)
Nicolaus Copernicus (1508–14)
Andreas Vesalius (1543)
Galileo (1580s–1630s)
Johannes Kepler (1596–1611)
Blaise Pascal (1640s–50s)
Isaac Newton (1665–1704)
Benjamin Franklin (1752)
Benjamin Banneker (1790s)
Caroline Herschel (1787–1828)

1800s

Sophie Germain (1800s–20s)
Mary Anning (1820s–40s)
Maria Mitchell (1847)
Louis Pasteur (1847–85)
Charles Darwin (1858)
Mary Edwards Walker (1863–65)
Thomas Edison (1869–1920s)
Alexander Graham Bell (1876)
Nikola Tesla (1882–1910s)
Elizabeth Blackwell (late 1800s)
Susan La Flesche Picotte (1889–1913)
Lewis Latimer (1890)
Wassaja (1890s)
Pierre Curie (1890s–1906)
Marie Curie (1890s–1911)
George Washington Carver (1890s–1940s)

1900s and Beyond

Eugène Marais (early 1900s)
Guglielmo Marconi (1901)
Bertha Van Hoosen (1902–51)
Albert Einstein (1905)
Charles Henry Turner (1907–10)
Niels Bohr (1910s–40s)
Alice Ball (1915–16)
Joan Beauchamp Procter (1920s)
Margaret Chung (1920s–40s)
Frederick Grant Banting (1921–23)
Te Rangi Hīroa (1922–27)
Raymond Dart (1924)
Alexander Fleming (1928)
Margaret Mead (1928–60s)
Frédéric Joliot (1934)
Irène Joliot (1934)
Percy Julian (1935)
Max Theiler (1937)
Enrico Fermi (1942)
Ruth Benedict (1930s–40s)
Charles Richard Drew (1930s–40s)
Alan Turing (1940s)
Maria Goeppert Mayer (1940s–50s)
Edward Teller (1940s–50s)
Dorothy Crowfoot Hodgkin (1940s–60s)
J. Robert Oppenheimer (1940s–60s)
Chien-Shiung Wu (1940s–60s)
Marie Tharp (1940s–70s)
Jonas Salk (1942–55)
Robert Broom (1947)
Mary Douglas Leakey (1948 and 1978)
Eugenie Clark (1948–92)
Stephanie Kwolek (1950s–60s)
Ruth Benerito (1950s–80s)
Aaron Klug (1950s–80s)
Nancy Grace Roman (1950s–90s)
Francis Crick (1951–62)
James Watson (1951–62)
Virginia Apgar (1952)
Jane Goodall (1960–75)
Allan Cormack (1960s)
Mary Jackson (1960s)
Katherine Johnson (1960s)
Louis Leakey (1960s)
Jacques Piccard (1960s)
Dorothy Vaughan (1960s)
Richard Leakey (1960s–70s)
Gladys West (1960s–80s)
Rachel Carson (1962)
Phillip Tobias (1964 and 1995)
Dian Fossey (1966–83)
Robert Ballard (1970s–80s)
Christine Darden (1970s–80s)
Fred Hollows (1970s–80s)
Sally Ride (1970s–80s)
Richard Dawkins (1976)
Victor Chang (1980s)
Steven Chu (1980s)
Mae Jemison (1980s–90s)
Charles Bolden (1980s–90s)
Ronald McNair (1984)
Alexa Canady (1984–2000s)
Benjamin Carson (1987)
Patricia Bath (1988)
Temple Grandin (1990–)
Joycelyn Elders (1993–94)
Meave Leakey (1994)
Regina Benjamin (2009–13)
Anthony Fauci (1980s–2020s)

Scientists by Subject Studied

Some scientists, including Aristotle, Hypatia, al-Khwarizmi, Galileo, and Marie Curie, studied more than one subject of science in depth. Most others focused on a particular subject. The lists here group scientists by the subject that played a main role in their studies.

Astronomy

Aristarchus of Samos
Benjamin Banneker
Nicolaus Copernicus
Galileo
Caroline Herschel
Johannes Kepler
Maria Mitchell
Ptolemy
Nancy Grace Roman
Biology
Aristotle
Alexa Canady
Rachel Carson
Eugenie Clark
Charles Darwin
Richard Dawkins
Dian Fossey
Jane Goodall
Temple Grandin
Leonardo da Vinci
Eugène Marais
Joan Beauchamp Procter
Charles Henry Turner

Chemistry

Alice Ball
Ruth Benerito
George Washington Carver
Dorothy Crowfoot Hodgkin
Mae Jemison
Frédéric Joliot
Irène Joliot
Percy Julian
Aaron Klug
Stephanie Kwolek
Louis Pasteur
Earth Sciences
Robert Ballard
Jacques Piccard
Marie Tharp

Mathematics

al-Khwarizmi
Archimedes
Christine Darden
Euclid
Sophie Germain
Hypatia
Mary Jackson
Katherine Johnson
Blaise Pascal
Plato
Alan Turing
Dorothy Vaughan
Gladys West
Medicine
Virginia Apgar
Frederick Grant Banting
Patricia Bath
Regina Benjamin
Elizabeth Blackwell
Benjamin Carson
Victor Chang
Margaret Chung
Francis Crick
Charles Richard Drew
Joycelyn Elders
Anthony Fauci
Alexander Fleming
Fred Hollows
Susan La Flesche Picotte
Jonas Salk
Max Theiler
Bertha Van Hoosen
Andreas Vesalius
Mary Edwards Walker
Wassaja
James Watson

Paleontology and Anthropology

Mary Anning
Ruth Benedict
Robert Broom
Raymond Dart
Te Rangi Hīroa
Louis Leakey
Mary Douglas Leakey
Meave Leakey
Richard Leakey
Margaret Mead
Phillip Tobias

Physics

Alexander Graham Bell
Niels Bohr
Steven Chu
Allan Cormack
Marie Curie
Pierre Curie
Thomas Edison
Albert Einstein
Enrico Fermi
Lewis Latimer
Guglielmo Marconi
Maria Goeppert Mayer
Ronald McNair
Isaac Newton
J. Robert Oppenheimer
Sally Ride
Edward Teller
Nikola Tesla
Chien-Shiung Wu

Health-care-researchers-working-in-life-science-laboratory-1120-scaled.jpeg

Jai Ganesh · Yesterday 00:01:23

2303) Kinesiology

Gist

Kinesiology means 'the study of movement'. The term is also used by complementary medicine practitioners to describe a form of therapy that uses muscle monitoring (biofeedback) to look at what may be causing 'imbalances' in the body and attempts to relieve these imbalances.

Summary

Kinesiology is the Study of the mechanics and anatomy of human movement and their roles in promoting health and reducing disease. Kinesiology has direct applications to fitness and health, including developing exercise programs for people with and without disabilities, preserving the independence of older people, preventing disease due to trauma and neglect, and rehabilitating people after disease or injury. Kinesiologists also develop more accessible furniture and environments for people with limited movement and find ways to enhance individual and team efficiency. Kinesiology research encompasses the biochemistry of muscle contraction and tissue fluids, bone mineralization, responses to exercise, how physical skills are developed, work efficiency, and the anthropology of play.

Details

Kinesiology is the scientific study of human body movement. Kinesiology addresses physiological, anatomical, biomechanical, pathological, neuropsychological principles and mechanisms of movement. Applications of kinesiology to human health include biomechanics and orthopedics; strength and conditioning; sport psychology; motor control; skill acquisition and motor learning; methods of rehabilitation, such as physical and occupational therapy; and sport and exercise physiology. Studies of human and animal motion include measures from motion tracking systems, electrophysiology of muscle and brain activity, various methods for monitoring physiological function, and other behavioral and cognitive research techniques.

Basics

Kinesiology studies the science of human movement, performance, and function by applying the fundamental sciences of Cell Biology, Molecular Biology, Chemistry, Biochemistry, Biophysics, Biomechanics, Biomathematics, Biostatistics, Anatomy, Physiology, Exercise Physiology, Pathophysiology, Neuroscience, and Nutritional science. A bachelor's degree in kinesiology can provide strong preparation for graduate study in medical school, biomedical research, as well as in professional programs.

The term "kinesiologist" is not a licensed nor professional designation in many countries, with the notable exception of Canada. Individuals with training in this area can teach physical education, work as personal trainers and sports coaches, provide consulting services, conduct research and develop policies related to rehabilitation, human motor performance, ergonomics, and occupational health and safety. In North America, kinesiologists may study to earn a Bachelor of Science, Master of Science, or Doctorate of Philosophy degree in Kinesiology or a Bachelor of Kinesiology degree, while in Australia or New Zealand, they are often conferred an Applied Science (Human Movement) degree (or higher). Many doctoral-level faculty in North American kinesiology programs received their doctoral training in related disciplines, such as neuroscience, mechanical engineering, psychology, and physiology.

In 1965, the University of Massachusetts Amherst created the United States' first Department of Exercise Science (kinesiology) under the leadership of visionary researchers and academicians in the field of exercise science. In 1967, the University of Waterloo launched Canada's first kinesiology department.

Principles:

Adaptation through exercise

Adaptation through exercise is a key principle of kinesiology that relates to improved fitness in athletes as well as health and wellness in clinical populations. Exercise is a simple and established intervention for many movement disorders and musculoskeletal conditions due to the neuroplasticity of the brain and the adaptability of the musculoskeletal system. Therapeutic exercise has been shown to improve neuromotor control and motor capabilities in both normal and pathological populations.

There are many different types of exercise interventions that can be applied in kinesiology to athletic, normal, and clinical populations. Aerobic exercise interventions help to improve cardiovascular endurance. Anaerobic strength training programs can increase muscular strength, power, and lean body mass. Decreased risk of falls and increased neuromuscular control can be attributed to balance intervention programs. Flexibility programs can increase functional range of motion and reduce the risk of injury.

As a whole, exercise programs can reduce symptoms of depression and risk of cardiovascular and metabolic diseases. Additionally, they can help to improve quality of life, sleeping habits, immune system function, and body composition.

The study of the physiological responses to physical exercise and their therapeutic applications is known as exercise physiology, which is an important area of research within kinesiology.

Neuroplasticity

Adaptive plasticity along with practice in three levels. In behavior level, performance (e.g., successful rate, accuracy) improved after practice. In cortical level, motor representation areas of the acting muscles enlarged; functional connectivity between primary motor cortex (M1) and supplementary motor area (SMA) is strengthened. In neuronal level, the number of dendrites and neurotransmitter increase with practice.

Neuroplasticity is also a key scientific principle used in kinesiology to describe how movement and changes in the brain are related. The human brain adapts and acquires new motor skills based on this principle. The brain can be exposed to new stimuli and experiences and therefore learn from them and create new neural pathways hence leading to brain adaptation. These new adaptations and skills include both adaptive and maladaptive brain changes.

Adaptive plasticity

Recent[when?] empirical evidence indicates the significant impact of physical activity on brain function; for example, greater amounts of physical activity are associated with enhanced cognitive function in older adults. The effects of physical activity can be distributed throughout the whole brain, such as higher gray matter density and white matter integrity after exercise training, and/or on specific brain areas, such as greater activation in prefrontal cortex and hippocampus. Neuroplasticity is also the underlying mechanism of skill acquisition. For example, after long-term training, pianists showed greater gray matter density in sensorimotor cortex and white matter integrity in the internal capsule compared to non-musicians.

Maladaptive plasticity

Maladaptive plasticity is defined as neuroplasticity with negative effects or detrimental consequences in behavior. Movement abnormalities may occur among individuals with and without brain injuries due to abnormal remodeling in central nervous system. Learned non-use is an example commonly seen among patients with brain damage, such as stroke. Patients with stroke learned to suppress paretic limb movement after unsuccessful experience in paretic hand use; this may cause decreased neuronal activation at adjacent areas of the infarcted motor cortex.

There are many types of therapies that are designed to overcome maladaptive plasticity in clinic and research, such as constraint-induced movement therapy (CIMT), body weight support treadmill training (BWSTT) and virtual reality therapy. These interventions are shown to enhance motor function in paretic limbs and stimulate cortical reorganization in patients with brain damage.

Motor redundancy

* Motor redundancy is a widely used concept in kinesiology and motor control which states that, for any task the human body can perform, there are effectively an unlimited number of ways the nervous system could achieve that task. This redundancy appears at multiple levels in the chain of motor execution:

* Kinematic redundancy means that for a desired location of the endpoint (e.g. the hand or finger), there are many configurations of the joints that would produce the same endpoint location in space.

* Muscle redundancy means that the same net joint torque could be generated by many different relative contributions of individual muscles.

* Motor unit redundancy means that for the same net muscle force could be generated by many different relative contributions of motor units within that muscle.

The concept of motor redundancy is explored in numerous studies, usually with the goal of describing the relative contribution of a set of motor elements (e.g. muscles) in various human movements, and how these contributions can be predicted from a comprehensive theory. Two distinct (but not incompatible) theories have emerged for how the nervous system coordinates redundant elements: simplification and optimization. In the simplification theory, complex movements and muscle actions are constructed from simpler ones, often known as primitives or synergies, resulting in a simpler system for the brain to control. In the optimization theory, motor actions arise from the minimization of a control parameter, such as the energetic cost of movement or errors in movement performance.

Additional Information

Like a well-tuned instrument, your body needs precision, balance and optimal functioning to achieve greatness.

This is where the role of a kinesiologist becomes analogous to that of a skilled conductor orchestrating a symphony of movements. Just as a conductor harmonizes each instrument to create a masterpiece, a kinesiologist meticulously assesses the body’s movements, fine-tuning its mechanics to ensure peak performance.

If you’re intrigued by the captivating field of kinesiology and are wondering, “What is kinesiology?” then come along as we examine the historical roots, diverse applications and techniques of kinesiology: the science of movement.

Definition and History of Kinesiology

Kinesiology, rooted in the Greek term “kinesis,” signifying movement, and the suffix “-ology,” denoting a science or branch of knowledge, is fundamentally the study of human movement. Its historical roots trace back to the ancient philosopher Aristotle, often called the “Father of Kinesiology.” His work, “On the Motion of Animals” or “De Motu Animalium,” marked a pivotal moment by providing a geometric analysis of muscle actions, laying the foundation for studying movement.

Later on, in the 16th century, anatomist Andreas Vesalius laid the foundation for modern kinesiology by producing detailed drawings and descriptions of the human musculoskeletal system. Then, in the early 20th century, orthopedic surgeon R.W. Lovett laid the groundwork for muscle strength testing, developing a system that later found advancement in Henry and Florence Kendall’s 1949 book, “Muscle Testing and Function.”

The evolution of kinesiology as we recognize it today took another significant leap in 1964 when chiropractor George Goodheart introduced Applied Kinesiology. This approach involved studying muscle response, aligning with the term “kinesiology,” which denotes the study of movement. Goodheart’s innovative methods, effective in addressing complex health issues, were adopted across various healthcare fields.

Today, kinesiology is a thriving and multidisciplinary field, encompassing expertise from improving athletic performance and preventing injuries to developing assistive technologies for individuals with disabilities. Its trajectory highlights a continuous commitment to exploration and growth, leveraging centuries of research and innovation.

Principles of Kinesiology

Kinesiology refers to the study of movement. In American higher education, the term is used to describe a multifaceted field of study in which movement or physical activity is the intellectual focus. Physical activity includes exercising to improve health and fitness, learning movement skills, and engaging in activities of daily living, work, sport, dance, and play. Kinesiology is all-encompassing of the general population and relevant to everyone, not just sports enthusiasts or athletes. Special groups such as children and older adults as well as people with disabilities, injuries, or diseases can benefit from learning the principles of kinesiology and applying them to their daily activities and lives.

Learning and Practicing Kinesiology

Kinesiology is a common name for college and university academic departments that include many specialized areas of study in which the causes, processes, and consequences and contexts of physical activity are examined from different perspectives. The specialized areas of study apply knowledge, methods of inquiry, and principles from areas of study in the arts, humanities, sciences, and professional disciplines. These specialized areas include (but are not limited to) biomechanics, psychology of physical activity, exercise physiology, history of physical activity, measurement of physical activity, motor development, motor learning, and control, philosophy of physical activity, physical activity and public health, physical education pedagogy, sport management, sports medicine, and the sociology of physical activity. An interdisciplinary approach involving several of these areas is often used in addressing problems of importance to society.

Educational Path

A Kinesiology degree is an academic program that studies human movement, performance, and function. It integrates knowledge from various disciplines, including anatomy, physiology, biomechanics, psychology, neuroscience, and nutrition, to comprehensively understand how the human body moves and operates. This degree is designed to explore the principles of physical activity and its impact on health, wellness, and disease prevention.

Kinesiology programs often offer a variety of specializations, such as exercise science, physical education, rehabilitation, public health education, and sport management. These specializations allow students to tailor their education towards specific career goals in health promotion, fitness and wellness consulting, sports coaching, rehabilitation services (PT/OT/AT/ST/PA), and beyond.

The curriculum typically includes both theoretical coursework and practical experiences. Students engage in laboratory work, internships, and research projects that apply classroom knowledge to real-world settings. This hands-on approach not only enhances learning but also prepares graduates for professional practice in diverse settings, including hospitals, wellness centers, schools, sports organizations, and research institutions.

Graduates with a Kinesiology degree possess a deep understanding of the biomechanics of movement, the physiological responses to exercise, and strategies for promoting physical and mental well-being. They are equipped to pursue careers in health and fitness industries, rehabilitative sciences, sports coaching and performance analysis, health policy, and education, among others.

A Kinesiology degree offers a holistic and interdisciplinary approach to studying the body and its movements, aiming to improve human health, performance, and quality of life through physical activity.

Examples of courses in Kinesiology include:

* Introduction of Kinesiology: Explores the study of human movement, integrating principles from anatomy, physiology, biomechanics, and psychology to understand and enhance physical activity and health.
* Anatomy and Physiology: Detailed study of the human body's structure and function.
* Biomechanics: Examines the mechanical principles that govern human movement.
* Exercise Physiology: Looks at how the body responds and adapts to physical activity.
* Motor Learning and Control: Focuses on how we learn and refine movements.
* Sports Nutrition: Studies the role of diet in athletic performance and health.
* Strength and Conditioning: Teaches training principles to improve performance and prevent injuries.
* Health and Wellness Promotion: Focuses on strategies to encourage healthy lifestyles.
* Teaching Methods in Primary/Secondary Physical & Health Education: Curriculum and instructional models, national curriculum standards, teaching methods in PE.
* Motor Development: Knowledge and practice about physical growth, biological maturation, and motor development and their interrelationship in human performers.
Particular emphasis is placed on assessing and developing basic movement skills through programming strategies for individuals and large groups.
* Sports Psychology: Explores psychological factors that affect performance and physical activity.
* Esports: Introduction to esports, esports coaching, esports health and wellness, and moral principles in esports.
* Research Methods in Kinesiology: Provides an understanding of research design and analysis in studying human movement.

Jai Ganesh · Yesterday 18:19:26

2304) Hotelier

Gist

A hotelier is a person who runs or owns a hotel. If you stay at a hotel, you may never see the hotelier, who is responsible for hiring and managing staff and keeping things running smoothly.

They are responsible for ensuring the smooth running of the hotel, from guest services to facility maintenance, and are involved in a range of tasks such as hiring staff, managing finances, and promoting the hotel to potential guests.

Summary

A hotelier is a person who runs or owns a hotel. If you stay at a hotel, you may never see the hotelier, who is responsible for hiring and managing staff and keeping things running smoothly.

It's probably more common to use the term "hotel manager," but hotelier is a fancy way to refer to the person in charge of a hotel's operation. If you've got a complaint about your room, you might angrily demand to speak to the hotelier immediately. The word hotelier comes from the French hôtelier, "hotelkeeper or hotel proprietor," and its Old French root hostel, "a lodging."

Details

A hotel manager, hotelier, or lodging manager is a person who manages the operation of a hotel, motel, resort, or other lodging-related establishment. Management of a hotel operation includes, but is not limited to management of hotel staff, business management, upkeep and sanitary standards of hotel facilities, guest satisfaction and customer service, marketing management, sales management, revenue management, financial accounting, purchasing, and other functions. The title "hotel manager" or "hotelier" often refers to the hotel's general manager who serves as a hotel's head executive, though their duties and responsibilities vary depending on the hotel's size, purpose, and expectations from ownership. The hotel's general manager is often supported by subordinate department managers that are responsible for individual departments and key functions of the hotel operations.

Hotel management structure

The size and complexity of a hotel management organizational structure varies significantly depending on the size, features, and function of the hotel or resort. A small hotel operation normally may consist of a small core management team consisting of a hotel manager and a few key department supervisors who directly handle day-to-day operations. On the other hand, a large full-service hotel or resort complex often operates more similarly to a large corporation with an executive board headed by the general manager and consisting of key directors serving as heads of individual hotel departments. Each department at the large hotel or resort complex may normally consist of subordinate line-level managers and supervisors who handle day-to-day operations.

Administrative functions for a small-scale hotel such as accounting, payroll, and human resources may normally be handled by a centralized corporate office or solely by the hotel manager. Additional auxiliary functions such as security may be handled by third-party vendor services contracted by the hotel on an as-needed basis. Hotel management is necessary to implement standard operating procedures and actions as well as handling day-to-day operations.

Typical qualifications

The background and training required varies by the type of management position, size of operation, and duties involved. Industry experience has proven to be a basic qualification for nearly any management occupation within the lodging industry. A BS and a MS degree in Hospitality Management/or an equivalent Business degree is often strongly preferred by most employers in the industry but not always required.

A higher level graduate degree may be desired for a general manager type position, but is often not required with sufficient management experience and industry tenure. A graduate degree may however be required for a higher level corporate executive position or above such as a Regional Vice President who oversees multiple hotel properties and general managers.

Working conditions

Hotel managers are generally exposed to long shifts that include late hours, weekends, and holidays due to the 24-hour operation of a hotel. The common workplace environment in hotels is fast-paced, with high levels of interaction with guests, employees, investors, and other managers.

Upper management consisting of senior managers, department heads, and general managers may sometimes enjoy a more desirable work schedule consisting of a more traditional business day with occasional weekends and holidays off.

Depending on the size of the hotel, a typical hotel manager's day may include assisting with operational duties, managing employee performance, handling dissatisfied guests, managing work schedules, purchasing supplies, interviewing potential job candidates, conducting physical walks and inspections of the hotel facilities and public areas, and additional duties. These duties may vary each day depending on the needs of the property. The manager's responsibility also includes knowing about all current local events as well as the events being held on the hotel property. Managers are often required to attend regular department meetings, management meetings, training seminars for professional development, and additional functions. A hotel/casino property may require additional duties regarding special events being held on property for casino complimentary guests.

2020 coronavirus pandemic

Working conditions were increasingly difficult during the 2020 coronavirus pandemic. One CEO of a major hotel owner, Monty Bennett of Ashford Inc., told CBS News that he had to lay off or furlough 95% of his 7,000 U.S. workers. To save money, hotel management are compelled to reduce all discretionary operational and capital costs, and review or postpone maintenance and other capital investments whenever possible. By the second week of the major outbreak of the virus in the U.S., the industry asked Congress for $250 billion in bailouts for owners and employees because of financial setbacks and mass layoffs.

Salary expectations

The median annual wage in 2015 of the 48,400 lodging managers in the United States was $49,720.

Additional Information

Hotel Management involves the implementation of access control measures within a hotel building to regulate the entry of various individuals such as owners, staff, guests, visitors, and service providers, while ensuring security and convenience for legitimate occupants.

Hotel Building Access Control

There are many different people who may, at any one time, wish to enter a hotel building. They include hotel owners and management staff, hotel contractors (such as elevator technicians and engineering, maintenance, security, janitorial, and parking personnel), guests, visitors, salespersons, tradespeople (including construction workers, electricians, plumbers, carpenters, gardeners, telecommunications repair persons, persons replenishing vending machines, and others who service equipment within the hotel), building inspectors, couriers, delivery persons, solicitors,♦ sightseers, people who are lost, vagrants or homeless people, mentally disturbed individuals, vandals, suicidal persons, protestors, and daredevils. There may also be others who try to enter hotel parking areas, retail shops, restaurants, health clubs, business centers, recreational facilities, gyms, exercise rooms, function rooms, meeting rooms, or an individual guest room, with the sole purpose of committing a crime.

It is primarily the hotel owner and operator who determine the access control measures for this wide spectrum of persons. These measures aim to screen out unwanted persons or intruders and at the same time provide a minimum of inconvenience to hotel guests and legitimate visitors. Varying degrees of access control can be achieved using security staff—in some hotels known as a security officer, a security guard, a doorman, a concierge, or by another title that differs according to the respective duties and responsibilities—and various security measures.

Building access controls include vehicle access to parking lots, garages, and loading dock/shipping and receiving areas; pedestrian access to building lobbies, elevator lobbies, and passenger and freight/service elevators; and access routes to retail spaces, restaurants, promenades, mezzanines, atria, and maintenance areas.

Jai Ganesh · Today 00:05:00

2305) Geologist

Gist

A geologist is a scientist who studies the structure, composition, and history of Earth. Geologists incorporate techniques from physics, chemistry, biology, mathematics, and geography to perform research in the field and the laboratory. Geologists work in the energy and mining sectors to exploit natural resources.

The word geology means 'Study of the Earth'. Also known as geoscience or earth science, Geology is the primary Earth science and looks at how the earth formed, its structure and composition, and the types of processes acting on it.

Summary

Geologists are employed in a diverse range of jobs in many different industries. Some work in the field, some in offices and others have a mixture of both. In a nutshell, Geologists work to better understand the Earth, but what do they actually do?

Below are some examples of the tasks Geologists carry out in their respective industries.

Mapping & Fieldwork

This is a field-based task many geologists undertake. Different types of field mapping will look for different aspects of the rocks of a particular area.

* Field mapping looks at the particular rock types and geological structures of an area and how they all relate to one another – the aim is to produce a ‘geological map’. It is undertaken by geology students and geoscientists who work for universities, mining and exploration companies or some oil and gas companies.
* Sampling trips are common for researchers and geological exploration companies.

Logging

Again, this is often a field-based activity undertaken with geological drilling. Geologists describe rock extracted by drills to understand the geology below the surface. Logging of sedimentary or volcanic rocks above ground is also used to study past environmental changes or accurately record sampling locations.

Some types of logging include:

* Rock core logging (or rock chip logging) for mining and exploration companies
* Mud logging is undertaken for oil and gas exploration
* Geotechnical logging – this assesses how strong or weak rocks are below the ground using rock core.

Laboratory Work

Many geologists undertake laboratory work in their careers. A lot of what we know about the geology of the world and other planets has been discovered in laboratories. Researchers and those who work for some geology-related companies work in laboratories. There are also some geoscientists employed specifically in commercial laboratories that a huge number of geology-related companies (e.g. mining, oil & gas, engineering and environmental companies) use to acquire data.

Laboratory work can include:

* Geochemical analyses – using chemical methods to reveal details about samples (such as their metal content or the quality of oil).
* Geomechanical tests – testing the strength of rocks.

Computer-based work

All geologists will do a lot of their work on computer, often using specialist software, mostly in offices but field-based computer work is becoming more common. This can include:

* Geographical Information Systems (GIS) – essentially, this is field mapping on computers – producing a digital database of the field data acquired by geologists.
* Database management – Geologists spend a lot of time ensuring databases are up to date. This can be vital for the modelling processes described below.
* Modelling programs – this has become increasingly important for geologists, both those who do research and in commercial companies. This means many geologists are trained in specialist software or programming.

Details

A geologist is a scientist who studies the structure, composition, and history of Earth. Geologists incorporate techniques from physics, chemistry, biology, mathematics, and geography to perform research in the field and the laboratory. Geologists work in the energy and mining sectors to exploit natural resources. They monitor environmental hazards such as earthquakes, volcanoes, tsunamis and landslides. Geologists are also important contributors to climate change discussions.

History

James Hutton is often viewed as the first modern geologist. In 1785 he presented a paper entitled Theory of the Earth to the Royal Society of Edinburgh. In his paper, he explained his theory that the Earth must be much older than had previously been supposed to allow enough time for mountains to be eroded and for sediments to form new rocks at the bottom of the sea, which in turn were raised up to become dry land. Hutton published a two-volume version of his ideas in 1795 (Vol. 1, Vol. 2). Followers of Hutton were known as Plutonists because they believed that some rocks were formed by vulcanism, which is the deposition of lava from volcanoes, as opposed to the Neptunists, led by Abraham Werner, who believed that all rocks had settled out of a large ocean whose level gradually dropped over time.

The first geological map of the United States was produced in 1809 by William Maclure. In 1807, Maclure commenced the self-imposed task of making a geological survey of the United States. Almost every state in the Union was traversed and mapped by him; the Allegheny Mountains being crossed and recrossed some 50 times. The results of his unaided labors were submitted to the American Philosophical Society in a memoir entitled Observations on the Geology of the United States explanatory of a Geological Map, and published in the Society's Transactions, together with the nation's first geological map. This antedates William Smith's geological map of England by six years, although it was constructed using a different classification of rocks.

Sir Charles Lyell first published his famous book, Principles of Geology, in 1830. This book, which influenced the thought of Charles Darwin, successfully promoted the doctrine of uniformitarianism. This theory states that slow geological processes have occurred throughout the Earth's history and are still occurring today. In contrast, catastrophism is the theory that Earth's features formed in single, catastrophic events and remained unchanged thereafter. Though Hutton believed in uniformitarianism, the idea was not widely accepted at the time.

Education

For an aspiring geologist, training typically includes significant coursework in physics, mathematics, and chemistry, in addition to classes offered through the geology department; historical and physical geology, igneous and metamorphic petrology and petrography, hydrogeology, sedimentology, stratigraphy, mineralogy, palaeontology, physical geography and structural geology are among the many required areas of study. Most geologists also need skills in GIS and other mapping techniques. Geology students often spend portions of the year, especially the summer though sometimes during a January term, living and working under field conditions with faculty members (often referred to as "field camp"). Many non-geologists often take geology courses or have expertise in geology that they find valuable to their fields; this is common in the fields of geography, engineering, chemistry, urban planning, environmental studies, among others.

Specialization

Geologists, can be generally identified as a specialist in one or more of the various geoscience disciplines, such as a geophysicist or geochemist. Geologists may concentrate their studies or research in one or more of the following disciplines:

* Economic geology: the study of ore genesis, and the mechanisms of ore creation, geostatistics.
* Engineering geology: application of the geologic sciences to engineering practice for the purpose of assuring that the geologic factors affecting the location, design, construction, operation and maintenance of engineering works are recognized and adequately provided for;
* Geophysics: the applied branch deals with the application of physical methods such as gravity, seismicity, electricity, magnetic properties to study the earth.
* Geochemistry: the applied branch deals with the study of the chemical makeup and behaviour of rocks, and the study of the behaviour of their minerals.
* Geochronology: the study of isotope geology specifically toward determining the date within the past of rock formation, metamorphism, mineralization and geological events (notably, meteorite impacts).
* Geomorphology: the study of landforms and the processes that create them.
* Hydrogeology: the study of the origin, occurrence and movement of groundwater water in a subsurface geological system.
* Igneous petrology: the study of igneous processes such as igneous differentiation, fractional crystallization, intrusive and volcanological phenomena.
* Isotope geology: the case of the isotopic composition of rocks to determine the processes of rock and planetary formation.
* Metamorphic petrology: the study of the effects of metamorphism on minerals and rocks.
Marine geology: the study of the seafloor; involves geophysical, geochemical, sedimentological and paleontological investigations of the ocean floor and coastal margins. Marine geology has strong ties to physical oceanography and plate tectonics.
* Mineralogy: the study of the chemistry, crystal structure, and physical (including optical) properties of minerals and mineralized artifacts. Specific studies within mineralogy include the processes of mineral origin and formation, classification of minerals, their geographical distribution, as well as their utilization.
* Palaeoclimatology: the application of geological science to determine the climatic conditions present in the Earth's atmosphere within the Earth's history.
* Palaeontology: the classification and taxonomy of fossils within the geological record and the construction of a palaeontological history of the Earth.
* Pedology: the study of soil, soil formation, and regolith formation.
* Petroleum geology: the study of sedimentary basins applied to the search for hydrocarbons (oil exploration).
* Planetary geology: the study of geosciences as it relates to other celestial bodies, namely planets and their moons. This includes the subdisciplines of lunar geology, selenology, and martian geology, areology.
* Sedimentology: the study of sedimentary rocks, strata, formations, eustasy and the processes of modern-day sedimentary and erosive systems.
* Seismology: the study of earthquakes.
* Structural geology: the study of folds, faults, foliation and rock microstructure to determine the deformational history of rocks and regions.
* Volcanology: the study of volcanoes, their eruptions, lavas, magma processes and hazards.

Employment

Professional geologists may work in the mining industry or in the associated area of mineral exploration. They may also work in oil and gas industry.

Some geologists also work for a wide range of government agencies, private firms, and non-profit and academic institutions. They are usually hired on a contract basis or hold permanent positions within private firms or official agencies (such as the Geological Survey and Mineral Exploration of Iran).

Local, state, and national governments hire geologists to work on geological projects that are of interest to the public community. The investigation of a country's natural resources is often a key role when working for government institutions; the work of the geologist in this field can be made publicly available to help the community make more informed decisions related to the exploitation of resources, management of the environment and the safety of critical infrastructure - all of which is expected to bring greater wellbeing to the country. This 'wellbeing' is often in the form of greater tax revenues from new or extended mining projects or through better infrastructure and/or natural disaster planning.

An engineering geologist is employed to investigate geologic hazards and geologic constraints for the planning, design and construction of public and private engineering projects, forensic and post-mortem studies, and environmental impact analysis. Exploration geologists use all aspects of geology and geophysics to locate and study natural resources. In many countries or U.S. states without specialized environmental remediation licensure programs, the environmental remediation field is often dominated by professional geologists, particularly hydrogeologists, with professional concentrations in this aspect of the field. Petroleum and mining companies use mudloggers, and large-scale land developers use the skills of geologists and engineering geologists to help them locate oil and minerals, adapt to local features such as karst topography or earthquake risk, and comply with environmental regulations.

Geologists in academia usually hold an advanced degree in a specialized area within their geological discipline and are employed by universities.

Additional Information

Geology is the fields of study concerned with the solid Earth. Included are sciences such as mineralogy, geodesy, and stratigraphy.

An introduction to the geochemical and geophysical sciences logically begins with mineralogy, because Earth’s rocks are composed of minerals—inorganic elements or compounds that have a fixed chemical composition and that are made up of regularly aligned rows of atoms. Today one of the principal concerns of mineralogy is the chemical analysis of the some 3,000 known minerals that are the chief constituents of the three different rock types: sedimentary (formed by diagenesis of sediments deposited by surface processes); igneous (crystallized from magmas either at depth or at the surface as lavas); and metamorphic (formed by a recrystallization process at temperatures and pressures in the Earth’s crust high enough to destabilize the parent sedimentary or igneous material). Geochemistry is the study of the composition of these different types of rocks.

During mountain building, rocks became highly deformed, and the primary objective of structural geology is to elucidate the mechanism of formation of the many types of structures (e.g., folds and faults) that arise from such deformation. The allied field of geophysics has several subdisciplines, which make use of different instrumental techniques. Seismology, for example, involves the exploration of the Earth’s deep structure through the detailed analysis of recordings of elastic waves generated by earthquakes and man-made explosions. Earthquake seismology has largely been responsible for defining the location of major plate boundaries and of the dip of subduction zones down to depths of about 700 kilometres at those boundaries. In other subdisciplines of geophysics, gravimetric techniques are used to determine the shape and size of underground structures; electrical methods help to locate a variety of mineral deposits that tend to be good conductors of electricity; and paleomagnetism has played the principal role in tracking the drift of continents.

Geomorphology is concerned with the surface processes that create the landscapes of the world—namely, weathering and erosion. Weathering is the alteration and breakdown of rocks at the Earth’s surface caused by local atmospheric conditions, while erosion is the process by which the weathering products are removed by water, ice, and wind. The combination of weathering and erosion leads to the wearing down or denudation of mountains and continents, with the erosion products being deposited in rivers, internal drainage basins, and the oceans. Erosion is thus the complement of deposition. The unconsolidated accumulated sediments are transformed by the process of diagenesis and lithification into sedimentary rocks, thereby completing a full cycle of the transfer of matter from an old continent to a young ocean and ultimately to the formation of new sedimentary rocks. Knowledge of the processes of interaction of the atmosphere and the hydrosphere with the surface rocks and soils of the Earth’s crust is important for an understanding not only of the development of landscapes but also (and perhaps more importantly) of the ways in which sediments are created. This in turn helps in interpreting the mode of formation and the depositional environment of sedimentary rocks. Thus the discipline of geomorphology is fundamental to the uniformitarian approach to the Earth sciences according to which the present is the key to the past.

Geologic history provides a conceptual framework and overview of the evolution of the Earth. An early development of the subject was stratigraphy, the study of order and sequence in bedded sedimentary rocks. Stratigraphers still use the two main principles established by the late 18th-century English engineer and surveyor William Smith, regarded as the father of stratigraphy: (1) that younger beds rest upon older ones and (2) different sedimentary beds contain different and distinctive fossils, enabling beds with similar fossils to be correlated over large distances. Today biostratigraphy uses fossils to characterize successive intervals of geologic time, but as relatively precise time markers only to the beginning of the Cambrian Period, about 540,000,000 years ago. The geologic time scale, back to the oldest rocks, some 4,280,000,000 years ago, can be quantified by isotopic dating techniques. This is the science of geochronology, which in recent years has revolutionized scientific perception of Earth history and which relies heavily on the measured parent-to-daughter ratio of radiogenic isotopes.

Paleontology is the study of fossils and is concerned not only with their description and classification but also with an analysis of the evolution of the organisms involved. Simple fossil forms can be found in early Precambrian rocks as old as 3,500,000,000 years, and it is widely considered that life on Earth must have begun before the appearance of the oldest rocks. Paleontological research of the fossil record since the Cambrian Period has contributed much to the theory of evolution of life on Earth.

Several disciplines of the geologic sciences have practical benefits for society. The geologist is responsible for the discovery of minerals (such as lead, chromium, nickel, and tin), oil, gas, and coal, which are the main economic resources of the Earth; for the application of knowledge of subsurface structures and geologic conditions to the building industry; and for the prevention of natural hazards or at least providing early warning of their occurrence.

Astrogeology is important in that it contributes to understanding the development of the Earth within the solar system. The U.S. Apollo program of manned missions to the Moon, for example, provided scientists with firsthand information on lunar geology, including observations on such features as meteorite craters that are relatively rare on Earth. Unmanned space probes have yielded significant data on the surface features of many of the planets and their satellites. Since the 1970s even such distant planetary systems as those of Jupiter, Saturn, and Uranus have been explored by probes.

Study of the composition of the Earth:

Mineralogy

As a discipline, mineralogy has had close historical ties with geology. Minerals as basic constituents of rocks and ore deposits are obviously an integral aspect of geology. The problems and techniques of mineralogy, however, are distinct in many respects from those of the rest of geology, with the result that mineralogy has grown to be a large, complex discipline in itself.

About 3,000 distinct mineral species are recognized, but relatively few are important in the kinds of rocks that are abundant in the outer part of the Earth. Thus a few minerals such as the feldspars, quartz, and mica are the essential ingredients in granite and its near relatives. Limestones, which are widely distributed on all continents, consist largely of only two minerals, calcite and dolomite. Many rocks have a more complex mineralogy, and in some the mineral particles are so minute that they can be identified only through specialized techniques.

It is possible to identify an individual mineral in a specimen by examining and testing its physical properties. Determining the hardness of a mineral is the most practical way of identifying it. This can be done by using the Mohs scale of hardness, which lists 10 common minerals in their relative order of hardness: talc (softest with the scale number 1), gypsum (2), calcite (3), fluorite (4), apatite (5), orthoclase (6), quartz (7), topaz (8), corundum (9), and diamond (10). Harder minerals scratch softer ones, so that an unknown mineral can be readily positioned between minerals on the scale. Certain common objects that have been assigned hardness values roughly corresponding to those of the Mohs scale (e.g., fingernail [2.5], pocketknife blade [5.5], steel file [6.5]) are usually used in conjunction with the minerals on the scale for additional reference.

Other physical properties of minerals that aid in identification are crystal form, cleavage type, fracture, streak, lustre, colour, specific gravity, and density. In addition, the refractive index of a mineral can be determined with precisely calibrated immersion oils. Some minerals have distinctive properties that help to identify them. For example, carbonate minerals effervesce with dilute acids; halite is soluble in water and has a salty taste; fluorite (and about 100 other minerals) fluoresces in ultraviolet light; and uranium-bearing minerals are radioactive.

The science of crystallography is concerned with the geometric properties and internal structure of crystals. Because minerals are generally crystalline, crystallography is an essential aspect of mineralogy. Investigators in the field may use a reflecting goniometer that measures angles between crystal faces to help determine the crystal system to which a mineral belongs. Another instrument that they frequently employ is the X-ray diffractometer, which makes use of the fact that X-rays, when passing through a mineral specimen, are diffracted at regular angles. The paths of the diffracted rays are recorded on photographic film, and the positions and intensities of the resulting diffraction lines on the film provide a particular pattern. Every mineral has its own unique diffraction pattern, so crystallographers are able to determine not only the crystal structure of a mineral but the type of mineral as well.

When a complex substance such as a magma crystallizes to form igneous rock, the grains of different constituent minerals grow together and mutually interfere, with the result that they do not retain their externally recognizable crystal form. To study the minerals in such a rock, the mineralogist uses a petrographic microscope constructed for viewing thin sections of the rock, which are ground uniformly to a thickness of about 0.03 millimetre, in light polarized by two polarizing prisms in the microscope. If the rock is crystalline, its essential minerals can be determined by their peculiar optical properties as revealed in transmitted light under magnification, provided that the individual crystal grains can be distinguished. Opaque minerals, such as those with a high content of metallic elements, require a technique employing reflected light from polished surfaces. This kind of microscopic analysis has particular application to metallic ore minerals. The polarizing microscope, however, has a lower limit to the size of grains that can be distinguished with the eye; even the best microscopes cannot resolve grains less than about 0.5 micrometre (0.0005 millimetre) in diameter. For higher magnifications the mineralogist uses an electron microscope, which produces images with diameters enlarged tens of thousands of times.

The methods described above are based on a study of the physical properties of minerals. Another important area of mineralogy is concerned with the chemical composition of minerals. The primary instrument used is the electron microprobe. Here a beam of electrons is focused on a thin section of rock that has been highly polished and coated with carbon. The electron beam can be narrowed to a diameter of about one micrometre and thus can be focused on a single grain of a mineral, which can be observed with an ordinary optical microscope system. The electrons cause the atoms in the mineral under examination to emit diagnostic X-rays, the intensity and concentration of which are measured by a computer. Besides spot analysis, this method allows a mineral to be traversed for possible chemical zoning. Moreover, the concentration and relative distribution of elements such as magnesium and iron across the boundary of two coexisting minerals like garnet and pyroxene can be used with thermodynamic data to calculate the temperature and pressure at which minerals of this type crystallize.

Although the major concern of mineralogy is to describe and classify the geometrical, chemical, and physical properties of minerals, it is also concerned with their origin. Physical chemistry and thermodynamics are basic tools for understanding mineral origin. Some of the observational data of mineralogy are concerned with the behaviour of solutions in precipitating crystalline materials under controlled conditions in the laboratory. Certain minerals can be created synthetically under conditions in which temperature and concentration of solutions are carefully monitored. Other experimental methods include study of the transformation of solids at high temperatures and pressures to yield specific minerals or assemblages of minerals. Experimental data obtained in the laboratory, coupled with chemical and physical theory, enable the conditions of origin of many naturally occurring minerals to be inferred.

Petrology

Petrology is the study of rocks, and, because most rocks are composed of minerals, petrology is strongly dependent on mineralogy. In many respects mineralogy and petrology share the same problems; for example, the physical conditions that prevail (pressure, temperature, time, and presence or absence of water) when particular minerals or mineral assemblages are formed. Although petrology is in principle concerned with rocks throughout the crust, as well as with those of the inner depths of the Earth, in practice the discipline deals mainly with those that are accessible in the outer part of the Earth’s crust. Rock specimens obtained from the surface of the Moon and from other planets are also proper considerations of petrology. Fields of specialization in petrology correspond to the aforementioned three major rock types—igneous, sedimentary, and metamorphic.

Igneous petrology

Igneous petrology is concerned with the identification, classification, origin, evolution, and processes of formation and crystallization of the igneous rocks. Most of the rocks available for study come from the Earth’s crust, but a few, such as eclogites, derive from the mantle. The scope of igneous petrology is very large because igneous rocks make up the bulk of the continental and oceanic crusts and of the mountain belts of the world, which range in age from early Archean to Neogene, and they also include the high-level volcanic extrusive rocks and the plutonic rocks that formed deep within the crust. Of utmost importance to igneous petrologic research is geochemistry, which is concerned with the major- and trace-element composition of igneous rocks as well as of the magmas from which they arose. Some of the major problems within the scope of igneous petrology are: (1) the form and structure of igneous bodies, whether they be lava flows or granitic intrusions, and their relations to surrounding rocks (these are problems studied in the field); (2) the crystallization history of the minerals that make up igneous rocks (this is determined with the petrographic polarizing microscope); (3) the classification of rocks based on textural features, grain size, and the abundance and composition of constituent minerals; (4) the fractionation of parent magmas by the process of magmatic differentiation, which may give rise to an evolutionary sequence of genetically related igneous products; (5) the mechanism of generation of magmas by partial melting of the lower continental crust, suboceanic and subcontinental mantle, and subducting slabs of oceanic lithosphere; (6) the history of formation and the composition of the present oceanic crust determined on the basis of data from the Integrated Ocean Drilling Program (IODP); (7) the evolution of igneous rocks through geologic time; (8) the composition of the mantle from studies of the rocks and mineral chemistry of eclogites brought to the surface in kimberlite pipes; (9) the conditions of pressure and temperature at which different magmas form and at which their igneous products crystallize (determined from high-pressure experimental petrology).

The basic instrument of igneous petrology is the petrographic polarizing microscope, but the majority of instruments used today have to do with determining rock and mineral chemistry. These include the X-ray fluorescence spectrometer, equipment for neutron activation analysis, induction-coupled plasma spectrometer, electron microprobe, ionprobe, and mass spectrometer. These instruments are highly computerized and automatic and produce analyses rapidly (see below Geochemistry). Complex high-pressure experimental laboratories also provide vital data.

With a vast array of sophisticated instruments available, the igneous petrologist is able to answer many fundamental questions. Study of the ocean floor has been combined with investigation of ophiolite complexes, which are interpreted as slabs of ocean floor that have been thrust onto adjacent continental margins. An ophiolite provides a much deeper section through the ocean floor than is available from shallow drill cores and dredge samples from the extant ocean floor. These studies have shown that the topmost volcanic layer consists of tholeiitic basalt or mid-ocean ridge basalt that crystallized at an accreting rift or ridge in the middle of an ocean. A combination of mineral chemistry of the basalt minerals and experimental petrology of such phases allows investigators to calculate the depth and temperature of the magma chambers along the mid-ocean ridge. The depths are close to six kilometres, and the temperatures range from 1,150 °C to 1,279 °C. Comprehensive petrologic investigation of all the layers in an ophiolite makes it possible to determine the structure and evolution of the associated magma chamber.

In 1974 B.W. Chappell and A.J.R. White discovered two major and distinct types of granitic rock—namely, I- and S-type granitoids. The I-type has strontium-87/strontium-86 ratios lower than 0.706 and contains magnetite, titanite, and allanite but no muscovite. These rocks formed above subduction zones in island arcs and active (subducting) continental margins and were ultimately derived by partial melting of mantle and subducted oceanic lithosphere. In contrast, S-type granitoids have strontium-87/strontium-86 ratios higher than 0.706 and contain muscovite, ilmenite, and monazite. These rocks were formed by partial melting of lower continental crust. Those found in the Himalayas were formed during the Miocene Epoch some 20,000,000 years ago as a result of the penetration of India into Asia, which thickened the continental crust and then caused its partial melting.

In the island arcs and active continental margins that rim the Pacific Ocean, there are many different volcanic and plutonic rocks belonging to the calc-alkaline series. These include basalt; andesite; dacite; rhyolite; ignimbrite; diorite; granite; peridotite; gabbro; and tonalite, trondhjemite, and granodiorite (TTG). They occur typically in vast batholiths, which may reach several thousand kilometres in length and contain more than 1,000 separate granitic bodies. These TTG calc-alkaline rocks represent the principal means of growth of the continental crust throughout the whole of geologic time. Much research is devoted to them in an effort to determine the source regions of their parent magmas and the chemical evolution of the magmas. It is generally agreed that these magmas were largely derived by the melting of a subducted oceanic slab and the overlying hydrated mantle wedge. One of the major influences on the evolution of these rocks is the presence of water, which was derived originally from the dehydration of the subducted slab.

Sedimentary petrology

The field of sedimentary petrology is concerned with the description and classification of sedimentary rocks, interpretation of the processes of transportation and deposition of the sedimentary materials forming the rocks, the environment that prevailed at the time the sediments were deposited, and the alteration (compaction, cementation, and chemical and mineralogical modification) of the sediments after deposition.

There are two main branches of sedimentary petrology. One branch deals with carbonate rocks, namely limestones and dolomites, composed principally of calcium carbonate (calcite) and calcium magnesium carbonate (dolomite). Much of the complexity in classifying carbonate rocks stems partly from the fact that many limestones and dolomites have been formed, directly or indirectly, through the influence of organisms, including bacteria, lime-secreting algae, various shelled organisms (e.g., mollusks and brachiopods), and by corals. In limestones and dolomites that were deposited under marine conditions, commonly in shallow warm seas, much of the material initially forming the rock consists of skeletons of lime-secreting organisms. In many examples, this skeletal material is preserved as fossils. Some of the major problems of carbonate petrology concern the physical and biological conditions of the environments in which carbonate material has been deposited, including water depth, temperature, degree of illumination by sunlight, motion by waves and currents, and the salinity and other chemical aspects of the water in which deposition occurred.

The other principal branch of sedimentary petrology is concerned with the sediments and sedimentary rocks that are essentially noncalcareous. These include sands and sandstones, clays and claystones, siltstones, conglomerates, glacial till, and varieties of sandstones, siltstones, and conglomerates (e.g., the graywacke-type sandstones and siltstones). These rocks are broadly known as clastic rocks because they consist of distinct particles or clasts. Clastic petrology is concerned with classification, particularly with respect to the mineral composition of fragments or particles, as well as the shapes of particles (angular versus rounded), and the degree of homogeneity of particle sizes. Other main concerns of clastic petrology are the mode of transportation of sedimentary materials, including the transportation of clay, silt, and fine sand by wind; and the transportation of these and coarser materials through suspension in water, through traction by waves and currents in rivers, lakes, and seas, and sediment transport by ice.

Sedimentary petrology also is concerned with the small-scale structural features of sediments and sedimentary rocks. Features that can be conveniently seen in a specimen held in the hand are within the domain of sedimentary petrology. These features include the geometrical attitude of mineral grains with respect to each other, small-scale cross stratification, the shapes and interconnections of pore spaces, and the presence of fractures and veinlets.

Instruments and methods used by sedimentary petrologists include the petrographic microscope for description and classification, X-ray mineralogy for defining fabrics and small-scale structures, physical model flume experiments for studying the effects of flow as an agent of transport and the development of sedimentary structures, and mass spectrometry for calculating stable isotopes and the temperatures of deposition, cementation, and diagenesis. Wet-suit diving permits direct observation of current processes on coral reefs, and manned submersibles enable observation at depth on the ocean floor and in mid-oceanic ridges.

The plate-tectonic theory has given rise to much interest in the relationships between sedimentation and tectonics, particularly in modern plate-tectonic environments—e.g., spreading-related settings (intracontinental rifts, early stages of intercontinental rifting such as the Red Sea, and late stages of intercontinental rifting such as the margins of the present Atlantic Ocean), mid-oceanic settings (ridges and transform faults), subduction-related settings (volcanic arcs, fore-arcs, back-arcs, and trenches), and continental collision-related settings (the Alpine-Himalayan belt and late orogenic basins with molasse [i.e., thick association of clastic sedimentary rocks consisting chiefly of sandstones and shales]). Today many subdisciplines of sedimentary petrology are concerned with the detailed investigation of the various sedimentary processes that occur within these plate-tectonic environments.

Metamorphic petrology

Metamorphism means change in form. In geology the term is used to refer to a solid-state recrystallization of earlier igneous, sedimentary, or metamorphic rocks. There are two main types of metamorphism: (1) contact metamorphism, in which changes induced largely by increase in temperature are localized at the contacts of igneous intrusions; and (2) regional metamorphism, in which increased pressure and temperature have caused recrystallization over extensive regions in mountain belts. Other types of metamorphism include local effects caused by deformation in fault zones, burning oil shales, and thrusted ophiolite complexes; extensive recrystallization caused by high heat flow in mid-ocean ridges; and shock metamorphism induced by high-pressure impacts of meteorites in craters on the Earth and Moon.

Metamorphic petrology is concerned with field relations and local tectonic environments; the description and classification of metamorphic rocks in terms of their texture and chemistry, which provides information on the nature of the premetamorphic material; the study of minerals and their chemistry (the mineral assemblages and their possible reactions), which yields data on the temperatures and pressures at which the rocks recrystallized; and the study of fabrics and the relations of mineral growth to deformation stages and major structures, which provides information about the tectonic conditions under which regional metamorphic rocks formed.

A supplement to metamorphism is metasomatism: the introduction and expulsion of fluids and elements through rocks during recrystallization. When new crust is formed and metamorphosed at a mid-oceanic ridge, seawater penetrates into the crust for a few kilometres and carries much sodium with it. During formation of a contact metamorphic aureole around a granitic intrusion, hydrothermal fluids carrying elements such as iron, boron, and fluorine pass from the granite into the wall rocks. When the continental crust is thickened, its lower part may suffer dehydration and form granulites. The expelled fluids, carrying such heat-producing elements as rubidium, uranium, and thorium migrate upward into the upper crust. Much petrologic research is concerned with determining the amount and composition of fluids that have passed through rocks during these metamorphic processes.

The basic instrument used by the metamorphic petrologist is the petrographic microscope, which allows detailed study and definition of mineral types, assemblages, and reactions. If a heating/freezing stage is attached to the microscope, the temperature of formation and composition of fluid inclusions within minerals can be calculated. These inclusions are remnants of the fluids that passed through the rocks during the final stages of their recrystallization. The electron microprobe is widely used for analyzing the composition of the component minerals. The petrologist can combine the mineral chemistry with data from experimental studies and thermodynamics to calculate the pressures and temperatures at which the rocks recrystallized. By obtaining information on the isotopic age of successive metamorphic events with a mass spectrometer, pressure–temperature–time curves can be worked out. These curves chart the movement of the rocks over time as they were brought to the surface from deep within the continental crust; this technique is important for understanding metamorphic processes. Some continental metamorphic rocks that contain diamonds and coesites (ultrahigh pressure minerals) have been carried down subduction zones to a depth of at least 100 kilometres (60 miles), brought up, and often exposed at the present surface within resistant eclogites of collisional orogenic belts—such as the Swiss Alps, the Himalayas, the Kokchetav metamorphic terrane in Kazakhstan, and the Variscan belt in Germany. These examples demonstrate that metamorphic petrology plays a key role in unraveling tectonic processes in mountain belts that have passed through the plate-tectonic cycle of events.

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