Edward Ching-Te 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 A meteorite is a rock (geology), rock that originated in outer space and has fallen to the surface of a planet or Natural satellite, moon. When the original object enters the atmosphere, various factors such as friction, pressure, and chemical ...

impacts on the Earth's crust. Born in

Suzhou Suzhou is a major prefecture-level city in southern Jiangsu province, China. As part of the Yangtze Delta megalopolis, it is a major economic center and focal point of trade and commerce. Founded in 514 BC, Suzhou rapidly grew in size by the ...

China China, officially the People's Republic of China (PRC), is a country in East Asia. With population of China, a population exceeding 1.4 billion, it is the list of countries by population (United Nations), second-most populous country after ...

, he was best known for discovering two high-pressure forms of

silica Silicon dioxide, also known as silica, is an oxide of silicon with the chemical formula , commonly found in nature as quartz. In many parts of the world, silica is the major constituent of sand. Silica is one of the most complex and abundant f ...

in nature:

coesite Coesite () is a form (polymorphism (materials science), polymorph) of silicon dioxide (silicon, Sioxide, O2) that is formed when very high pressure (2–3 gigapascals), and moderately high temperature (), are applied to quartz. Coesite was first ...

and stishovite.

Early life

Chao was born in

. He was the son of theologian T. C. Chao.

Career

Chao came to the

United States The United States of America (USA), also known as the United States (U.S.) or America, is a country primarily located in North America. It is a federal republic of 50 U.S. state, states and a federal capital district, Washington, D.C. The 48 ...

in 1945 to teach Chinese to American troops. He then attended the

University of Chicago The University of Chicago (UChicago, Chicago, or UChi) is a Private university, private research university in Chicago, Illinois, United States. Its main campus is in the Hyde Park, Chicago, Hyde Park neighborhood on Chicago's South Side, Chic ...

and was granted a PhD in geology in 1948. In 1949, he was employed by the

United States Geological Survey The United States Geological Survey (USGS), founded as the Geological Survey, is an agency of the U.S. Department of the Interior whose work spans the disciplines of biology, geography, geology, and hydrology. The agency was founded on Mar ...

(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 geology, economic geology, and

coal Coal is a combustible black or brownish-black sedimentary rock, formed as rock strata called coal seams. Coal is mostly carbon with variable amounts of other Chemical element, elements, chiefly hydrogen, sulfur, oxygen, and nitrogen. Coal i ...

petrology Petrology () is the branch of geology that studies rocks, their mineralogy, composition, texture, structure and the conditions under which they form. Petrology has three subdivisions: igneous, metamorphic, and sedimentary petrology. Igneous ...

. However, he was best known for his work on impact

geology Geology (). is a branch of natural science concerned with the Earth and other astronomical objects, the rocks of which they are composed, and the processes by which they change over time. Modern geology significantly overlaps all other Earth ...

and tektites. Shortly after he began work on tektites in 1960, Chao was given a sample of

sandstone Sandstone is a Clastic rock#Sedimentary clastic rocks, clastic sedimentary rock composed mainly of grain size, sand-sized (0.0625 to 2 mm) silicate mineral, silicate grains, Cementation (geology), cemented together by another mineral. Sand ...

from the vicinity of Meteor Crater,

Arizona Arizona is a U.S. state, state in the Southwestern United States, Southwestern region of the United States, sharing the Four Corners region of the western United States with Colorado, New Mexico, and Utah. It also borders Nevada to the nort ...

. From this material, he was able to isolate an unusual

mineral In geology and mineralogy, a mineral or mineral species is, broadly speaking, a solid substance with a fairly well-defined chemical composition and a specific crystal structure that occurs naturally in pure form.John P. Rafferty, ed. (2011): Mi ...

with high

refractive index In optics, the refractive index (or refraction index) of an optical medium is the ratio of the apparent speed of light in the air or vacuum to the speed in the medium. The refractive index determines how much the path of light is bent, or refrac ...

, which he showed to be a high-pressure polymorph of

silicon dioxide Silicon dioxide, also known as silica, is an oxide of silicon with the chemical formula , commonly found in nature as quartz. In many parts of the world, silica is the major constituent of sand. Silica is one of the most complex and abundan ...

. He named the new mineral

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.Chao, E.C.T. et al. (1962), Stishovite, a very high pressure new mineral from Meteor Crater, AZ, Journal of Geophysical Research: 67: 419–421. Coesite and stishovite became known as hallmarks of

impact crater An impact crater is a depression (geology), depression in the surface of a solid astronomical body formed by the hypervelocity impact event, impact of a smaller object. In contrast to volcanic craters, which result from explosion or internal c ...

events, which were essentially the only natural processes that produced high enough

pressure Pressure (symbol: ''p'' or ''P'') is the force applied perpendicular to the surface of an object per unit area over which that force is distributed. Gauge pressure (also spelled ''gage'' pressure)The preferred spelling varies by country and eve ...

s to transform ordinary

quartz Quartz is a hard, crystalline mineral composed of silica (silicon dioxide). The Atom, atoms are linked in a continuous framework of SiO4 silicon–oxygen Tetrahedral molecular geometry, tetrahedra, with each oxygen being shared between two tet ...

into both of these dense minerals. Chao went on to find coesite and stishovite in rocks from the Ries Crater in

Bavaria Bavaria, officially the Free State of Bavaria, is a States of Germany, state in the southeast of Germany. With an area of , it is the list of German states by area, largest German state by land area, comprising approximately 1/5 of the total l ...

Germany Germany, officially the Federal Republic of Germany, is a country in Central Europe. It lies between the Baltic Sea and the North Sea to the north and the Alps to the south. Its sixteen States of Germany, constituent states have a total popu ...

, establishing that this structure was also produced by impact cratering. Chao made many pioneering studies on tektites, and discovered the occurrence of

iron Iron is a chemical element; it has symbol Fe () and atomic number 26. It is a metal that belongs to the first transition series and group 8 of the periodic table. It is, by mass, the most common element on Earth, forming much of Earth's o ...

- nickel metal in specimens from the

Philippines The Philippines, officially the Republic of the Philippines, is an Archipelagic state, archipelagic country in Southeast Asia. Located in the western Pacific Ocean, it consists of List of islands of the Philippines, 7,641 islands, with a tot ...

. This helped establish that tektites were produced in

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 The Moon is Earth's only natural satellite. It Orbit of the Moon, orbits around Earth at Lunar distance, an average distance of (; about 30 times Earth diameter, Earth's diameter). The Moon rotation, rotates, with a rotation period (lunar ...

, 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 Apollo is one of the Twelve Olympians, Olympian deities in Ancient Greek religion, ancient Greek and Ancient Roman religion, Roman religion and Greek mythology, Greek and Roman mythology. Apollo has been recognized as a god of archery, mu ...

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 John Price Wetherill Medal from the Franklin Institute 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 Carbon () is a chemical element; it has chemical symbol, symbol C and atomic number 6. It is nonmetallic and tetravalence, tetravalent—meaning that its atoms are able to form up to four covalent bonds due to its valence shell exhibiting 4 ...

discovered at the Ries Crater, was also named in his honor.

References

External links

''Washington Post'' obituaryMeteoritical Society
{{DEFAULTSORT:Chao, Edward C. T. 1919 births 2008 deaths Chinese emigrants to the United States University of Chicago alumni Planetary scientists 20th-century American geologists United States Geological Survey personnel Barringer Medal winners