Edward C. T. Chao
Encyclopedia
Edward C. T. Chao (November 30, 1919 – February 3, 2008) was one of the founders of the field of impact metamorphism
, the study of the effects of meteorite
impacts on the Earth's crust.
Born in Suzhou
, China
, he was best known for discovering two high-pressure forms of silica in nature, coesite
and stishovite
.
in 1945 to teach Chinese to American troops. He then attended the University of Chicago
and was granted a PhD in geology in 1948. In 1949, he was employed by the United States Geological Survey
(USGS), where he spent his entire professional career until retiring in 1994.
, economic geology
, and coal
petrology
. However, he was best known for his work on impact
geology
and tektite
s. Shortly after he began work on tektites in 1960, Chao was given a sample of sandstone
from the vicinity of Meteor Crater
, Arizona
. From this material, he was able to isolate an unusual mineral
with high refractive index
, which he showed to be a high-pressure polymorph
of silicon dioxide
. He named the new mineral coesite
in honor of the scientist who had synthesized the same phase in the laboratory seven years earlier. Several years later, Chao found a second high-pressure polymorph of silica in these rocks. It too had been previously synthesized in laboratory studies, but was not known to occur in nature. He named this mineral stishovite
in honor of the person who had first made it, Russian physicist, Sergei Stishov. Coesite and stishovite became known as hallmarks of impact crater
events, which were essentially the only natural processes that produced high enough pressure
s to transform ordinary quartz
into both of these dense minerals. Chao went on to find coesite and stishovite in rocks from the Ries Crater
in Bavaria
, Germany
, establishing that this structure was also produced by impact cratering.
Chao made many pioneering studies on tektites, and discovered the occurrence of iron
-nickel
metal in specimens from the Philippines
. This helped establish that tektites were produced in meteorite
impacts. He also recognized that tektites showed evidence for passage through Earth's atmosphere, which led him to the conclusion that the impacts responsible for tektites occurred on the Moon
, a view that is no longer widely held among scientists.
His work on moon rocks included being a member of preliminary examination teams and
a principal investigator during the Apollo 11-17 research programs.
and, in 1992, the Barringer Medal
from the Meteoritical Society
for his work in impact geology. He was a recipient of the Alexander von Humboldt Foundation Senior U.S. Scientist Award, and had an asteroid named for him, 3906 Chao
. The mineral chaoite
, an impact-produced form of carbon
discovered at the Ries Crater
, was also named in his honor.
Shock metamorphism
Shock metamorphism or impact metamorphism describes the effects of shock-wave related deformation and heating during impact events. The formation of similar features during explosive volcanism is generally discounted due to the lack of metamorphic effects unequivocally associated with explosions...
, the study of the effects of meteorite
Meteorite
A meteorite is a natural object originating in outer space that survives impact with the Earth's surface. Meteorites can be big or small. Most meteorites derive from small astronomical objects called meteoroids, but they are also sometimes produced by impacts of asteroids...
impacts on the Earth's crust.
Born in Suzhou
Suzhou
Suzhou , previously transliterated as Su-chou, Suchow, and Soochow, is a major city located in the southeast of Jiangsu Province in Eastern China, located adjacent to Shanghai Municipality. The city is situated on the lower reaches of the Yangtze River and on the shores of Taihu Lake and is a part...
, China
China
Chinese civilization may refer to:* China for more general discussion of the country.* Chinese culture* Greater China, the transnational community of ethnic Chinese.* History of China* Sinosphere, the area historically affected by Chinese culture...
, he was best known for discovering two high-pressure forms of silica in nature, coesite
Coesite
Coesite[p] is a form of silicon dioxide SiO2 that is formed when very high pressure , and moderately high temperature , are applied to quartz. Coesite was first synthesized by Loring Coes, Jr., a chemist at the Norton Company, in 1953. In 1960, coesite was found by Edward C. T...
and stishovite
Stishovite
Stishovite is an extremely hard, dense tetragonal form of silicon dioxide. It was long considered the hardest known oxide; however, boron suboxide has recently been discovered to be much harder...
.
Career
Chao came to the United StatesUnited States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...
in 1945 to teach Chinese to American troops. He then attended the University of Chicago
University of Chicago
The University of Chicago is a private research university in Chicago, Illinois, USA. It was founded by the American Baptist Education Society with a donation from oil magnate and philanthropist John D. Rockefeller and incorporated in 1890...
and was granted a PhD in geology in 1948. In 1949, he was employed by the United States Geological Survey
United States Geological Survey
The United States Geological Survey is a scientific agency of the United States government. The scientists of the USGS study the landscape of the United States, its natural resources, and the natural hazards that threaten it. The organization has four major science disciplines, concerning biology,...
(USGS), where he spent his entire professional career until retiring in 1994.
Scientific contributions
Chao worked on a variety of topics over the course of his USGS career, including engineering geologyEngineering geology
Engineering geology is the 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...
, economic geology
Economic geology
Economic geology is concerned with earth materials that can be used for economic and/or industrial purposes. These materials include precious and base metals, nonmetallic minerals, construction-grade stone, petroleum minerals, coal, and water. The term commonly refers to metallic mineral deposits...
, and coal
Coal
Coal is a combustible black or brownish-black sedimentary rock usually occurring in rock strata in layers or veins called coal beds or coal seams. The harder forms, such as anthracite coal, can be regarded as metamorphic rock because of later exposure to elevated temperature and pressure...
petrology
Petrology
Petrology is the branch of geology that studies rocks, and the conditions in which rocks form....
. However, he was best known for his work on impact
Impact crater
In the broadest sense, the term impact crater can be applied to any depression, natural or manmade, resulting from the high velocity impact of a projectile with a larger body...
geology
Geology
Geology is the science comprising the study of solid Earth, the rocks of which it is composed, and the processes by which it evolves. Geology gives insight into the history of the Earth, as it provides the primary evidence for plate tectonics, the evolutionary history of life, and past climates...
and tektite
Tektite
Tektites are natural glass rocks up to a few centimeters in size, which most scientists argue were formed by the impact of large meteorites on Earth's surface. Tektites are typically black or olive-green, and their shape varies from rounded to irregular.Tektites are among the "driest" rocks, with...
s. Shortly after he began work on tektites in 1960, Chao was given a sample of sandstone
Sandstone
Sandstone is a sedimentary rock composed mainly of sand-sized minerals or rock grains.Most sandstone is composed of quartz and/or feldspar because these are the most common minerals in the Earth's crust. Like sand, sandstone may be any colour, but the most common colours are tan, brown, yellow,...
from the vicinity of Meteor Crater
Meteor Crater
Meteor Crater is a meteorite impact crater located approximately east of Flagstaff, near Winslow in the northern Arizona desert of the United States. Because the US Department of the Interior Division of Names commonly recognizes names of natural features derived from the nearest post office, the...
, Arizona
Arizona
Arizona ; is a state located in the southwestern region of the United States. It is also part of the western United States and the mountain west. The capital and largest city is Phoenix...
. From this material, he was able to isolate an unusual mineral
Mineral
A mineral is a naturally occurring solid chemical substance formed through biogeochemical processes, having characteristic chemical composition, highly ordered atomic structure, and specific physical properties. By comparison, a rock is an aggregate of minerals and/or mineraloids and does not...
with high refractive index
Refractive index
In optics the refractive index or index of refraction of a substance or medium is a measure of the speed of light in that medium. It is expressed as a ratio of the speed of light in vacuum relative to that in the considered medium....
, which he showed to be a high-pressure polymorph
Polymorphism (materials science)
Polymorphism in materials science is the ability of a solid material to exist in more than one form or crystal structure. Polymorphism can potentially be found in any crystalline material including polymers, minerals, and metals, and is related to allotropy, which refers to chemical elements...
of silicon dioxide
Silicon dioxide
The chemical compound silicon dioxide, also known as silica , is an oxide of silicon with the chemical formula '. It has been known for its hardness since antiquity...
. He named the new mineral coesite
Coesite
Coesite[p] is a form of silicon dioxide SiO2 that is formed when very high pressure , and moderately high temperature , are applied to quartz. Coesite was first synthesized by Loring Coes, Jr., a chemist at the Norton Company, in 1953. In 1960, coesite was found by Edward C. T...
in honor of the scientist who had synthesized the same phase in the laboratory seven years earlier. Several years later, Chao found a second high-pressure polymorph of silica in these rocks. It too had been previously synthesized in laboratory studies, but was not known to occur in nature. He named this mineral stishovite
Stishovite
Stishovite is an extremely hard, dense tetragonal form of silicon dioxide. It was long considered the hardest known oxide; however, boron suboxide has recently been discovered to be much harder...
in honor of the person who had first made it, Russian physicist, Sergei Stishov. Coesite and stishovite became known as hallmarks of impact crater
Impact crater
In the broadest sense, the term impact crater can be applied to any depression, natural or manmade, resulting from the high velocity impact of a projectile with a larger body...
events, which were essentially the only natural processes that produced high enough pressure
Pressure
Pressure is the force per unit area applied in a direction perpendicular to the surface of an object. Gauge pressure is the pressure relative to the local atmospheric or ambient pressure.- Definition :...
s to transform ordinary quartz
Quartz
Quartz is the second-most-abundant mineral in the Earth's continental crust, after feldspar. It is made up of a continuous framework of SiO4 silicon–oxygen tetrahedra, with each oxygen being shared between two tetrahedra, giving an overall formula SiO2. There are many different varieties of quartz,...
into both of these dense minerals. Chao went on to find coesite and stishovite in rocks from the Ries Crater
Nördlinger Ries
The Nördlinger Ries is a large circular depression in western Bavaria, Germany, located north of the Danube in the district of Donau-Ries. The city of Nördlingen is located about southwest of the centre of the depression....
in Bavaria
Bavaria
Bavaria, formally the Free State of Bavaria is a state of Germany, located in the southeast of Germany. With an area of , it is the largest state by area, forming almost 20% of the total land area of Germany...
, Germany
Germany
Germany , officially the Federal Republic of Germany , is a federal parliamentary republic in Europe. The country consists of 16 states while the capital and largest city is Berlin. Germany covers an area of 357,021 km2 and has a largely temperate seasonal climate...
, establishing that this structure was also produced by impact cratering.
Chao made many pioneering studies on tektites, and discovered the occurrence of iron
Iron
Iron is a chemical element with the symbol Fe and atomic number 26. It is a metal in the first transition series. It is the most common element forming the planet Earth as a whole, forming much of Earth's outer and inner core. It is the fourth most common element in the Earth's crust...
-nickel
Nickel
Nickel is a chemical element with the chemical symbol Ni and atomic number 28. It is a silvery-white lustrous metal with a slight golden tinge. Nickel belongs to the transition metals and is hard and ductile...
metal in specimens from the Philippines
Philippines
The Philippines , officially known as the Republic of the Philippines , is a country in Southeast Asia in the western Pacific Ocean. To its north across the Luzon Strait lies Taiwan. West across the South China Sea sits Vietnam...
. This helped establish that tektites were produced in meteorite
Meteorite
A meteorite is a natural object originating in outer space that survives impact with the Earth's surface. Meteorites can be big or small. Most meteorites derive from small astronomical objects called meteoroids, but they are also sometimes produced by impacts of asteroids...
impacts. He also recognized that tektites showed evidence for passage through Earth's atmosphere, which led him to the conclusion that the impacts responsible for tektites occurred on the Moon
Moon
The Moon is Earth's only known natural satellite,There are a number of near-Earth asteroids including 3753 Cruithne that are co-orbital with Earth: their orbits bring them close to Earth for periods of time but then alter in the long term . These are quasi-satellites and not true moons. For more...
, a view that is no longer widely held among scientists.
His work on moon rocks included being a member of preliminary examination teams and
a principal investigator during the Apollo 11-17 research programs.
Publications
- Comparative water-quality assessment of the Hai He River basin in the People's Republic of China and three similar basins in the United States U.S. Geological Survey Professional Paper No. 1647 (2001)
- Comparison of the Cretaceous-Tertiary boundary impact events and the 0.77-Ma Australasian tektite event; relevance to mass extinction U.S. Geological Survey Bulletin No. 2050 (1993)
- Allocation of subsamples of Apollo 17 lunar rocks from the boulder at station 7, for study by the International Consortium U.S. Geological Survey Open-File Report No. 78-511 (1978)
- Merumite; a complex assemblage of chromium minerals from Guyana U.S. Geological Survey Professional Paper No. 887 (1976)
Honors
Chao received the Wetherill Medal from the Franklin InstituteFranklin Institute
The Franklin Institute is a museum in Philadelphia, Pennsylvania, and one of the oldest centers of science education and development in the United States, dating to 1824. The Institute also houses the Benjamin Franklin National Memorial.-History:On February 5, 1824, Samuel Vaughn Merrick and...
and, in 1992, the Barringer Medal
Barringer Medal
The Barringer Medal recognizes outstanding work in the field of impact cratering and/or work that has led to a better understanding of impact phenomena. The Barringer Medal and Award were established to honor the memory of D. Moreau Barringer Sr. and his son D. Moreau Barringer Jr. and are...
from the Meteoritical Society
Meteoritical Society
The Meteoritical Society is a non-profit scholarly organization founded in 1933 to promote research and education in planetary science with emphasis on studies of meteorites and other extraterrestrial materials that further our understanding of the origin and history of the solar system.The...
for his work in impact geology. He was a recipient of the Alexander von Humboldt Foundation Senior U.S. Scientist Award, and had an asteroid named for him, 3906 Chao
3906 Chao
3906 Chao is a main-belt asteroid discovered on May 31, 1987 by Shoemaker, C. at Palomar.- External links :*...
. The mineral chaoite
Chaoite
Chaoite or white carbon is a mineral described as an allotrope of carbon whose existence is disputed. It was discovered in shock-fused graphite gneiss from the Ries crater in Bavaria. It has been described as slightly harder than graphite, with a reflection colour of grey to white...
, an impact-produced form of carbon
Carbon
Carbon is the chemical element with symbol C and atomic number 6. As a member of group 14 on the periodic table, it is nonmetallic and tetravalent—making four electrons available to form covalent chemical bonds...
discovered at the Ries Crater
Nördlinger Ries
The Nördlinger Ries is a large circular depression in western Bavaria, Germany, located north of the Danube in the district of Donau-Ries. The city of Nördlingen is located about southwest of the centre of the depression....
, was also named in his honor.