Thomas Edvard Krogh
Encyclopedia
Thomas Edvard "Tom" Krogh, FRSC
(1936 – April 29, 2008) was a geochronologist
and a former curator
for the Royal Ontario Museum
. He revolutionized the technique of radiometric
uranium-lead dating
with the development of new laboratory procedures and analytical methodologies. His discoveries have yielded an unprecedented level of precision in the dating of Precambrian
rocks. Krogh’s techniques have become the international defacto standard. The application of these techniques has provided a detailed understanding of the evolution of the Earth's Precambrian shield areas.
. Between 1955 and 1959, he studied geological engineering at Queen's University
and held several jobs. For the first two summers he worked as a Geological Assistant at Noranda Mines and Triana Explorations, respectively. Between 1957 and 1959, he worked as a Teaching Assistant at the university. In 1958, he supported the Geological Survey of Canada as a Geological Assistant. In 1959, he was a Senior Assistant for the Ontario Department of Mines. Krogh obtained a MSc
in geology from the university in 1960. He left Canada to study at the Massachusetts Institute of Technology
, where he continued to work whenever he was not studying. His first job was as a Teaching Assistant in Mineralogy, then as a Geologist
at Cominco
, then as a Research Assistant in Geochronology
. In 1964, he obtained his PhD
in geochronology.
He was a post-doctoral fellow in isotopic
geochemistry
until 1964 when he became a Scientific Staff Member. From 1964 to 1970, he specialized in Rubidium
–Strontium
dating of minerals and rocks. In 1970, he switched to specializing in the Uranium-Lead dating of zircon
s and other minerals.
In 1975, Krogh returned to Canada to work as the Associate Curator/Director of the Royal Ontario Museum’s Geochronology Laboratory. In 1976, he became a Professor in the Geology Department of the University of Toronto
. In 1978, he shifted to be Graduate Faculty Member with the university.
In 1979, he returned to the Royal Ontario Museum to be their Full Curator.
He worked on the Lithoprobe
project between 1991 and 1996.
Royal Society of Canada
The Royal Society of Canada , may also operate under the more descriptive name RSC: The Academies of Arts, Humanities and Sciences of Canada , is the oldest association of scientists and scholars in Canada...
(1936 – April 29, 2008) was a geochronologist
Geochronology
Geochronology is the science of determining the age of rocks, fossils, and sediments, within a certain degree of uncertainty inherent to the method used. A variety of dating methods are used by geologists to achieve this, and schemes of classification and terminology have been proposed...
and a former curator
Curator
A curator is a manager or overseer. Traditionally, a curator or keeper of a cultural heritage institution is a content specialist responsible for an institution's collections and involved with the interpretation of heritage material...
for the Royal Ontario Museum
Royal Ontario Museum
The Royal Ontario Museum is a museum of world culture and natural history in Toronto, Ontario, Canada. With its main entrance facing Bloor Street in Downtown Toronto, the museum is situated north of Queen's Park and east of Philosopher's Walk in the University of Toronto...
. He revolutionized the technique of radiometric
Radiometric dating
Radiometric dating is a technique used to date materials such as rocks, usually based on a comparison between the observed abundance of a naturally occurring radioactive isotope and its decay products, using known decay rates...
uranium-lead dating
Uranium-lead dating
Uranium-lead is one of the oldest and most refined of the radiometric dating schemes, with a routine age range of about 1 million years to over 4.5 billion years, and with routine precisions in the 0.1-1 percent range...
with the development of new laboratory procedures and analytical methodologies. His discoveries have yielded an unprecedented level of precision in the dating of Precambrian
Precambrian
The Precambrian is the name which describes the large span of time in Earth's history before the current Phanerozoic Eon, and is a Supereon divided into several eons of the geologic time scale...
rocks. Krogh’s techniques have become the international defacto standard. The application of these techniques has provided a detailed understanding of the evolution of the Earth's Precambrian shield areas.
Education
Krogh was born in Peterborough, OntarioPeterborough, Ontario
Peterborough is a city on the Otonabee River in southern Ontario, Canada, 125 kilometres northeast of Toronto. The population of the City of Peterborough was 74,898 as of the 2006 census, while the census metropolitan area has a population of 121,428 as of a 2009 estimate. It presently ranks...
. Between 1955 and 1959, he studied geological engineering at Queen's University
Queen's University
Queen's University, , is a public research university located in Kingston, Ontario, Canada. Founded on 16 October 1841, the university pre-dates the founding of Canada by 26 years. Queen's holds more more than of land throughout Ontario as well as Herstmonceux Castle in East Sussex, England...
and held several jobs. For the first two summers he worked as a Geological Assistant at Noranda Mines and Triana Explorations, respectively. Between 1957 and 1959, he worked as a Teaching Assistant at the university. In 1958, he supported the Geological Survey of Canada as a Geological Assistant. In 1959, he was a Senior Assistant for the Ontario Department of Mines. Krogh obtained a MSc
Master's degree
A master's is an academic degree granted to individuals who have undergone study demonstrating a mastery or high-order overview of a specific field of study or area of professional practice...
in geology from the university in 1960. He left Canada to study at the Massachusetts Institute of Technology
Massachusetts Institute of Technology
The Massachusetts Institute of Technology is a private research university located in Cambridge, Massachusetts. MIT has five schools and one college, containing a total of 32 academic departments, with a strong emphasis on scientific and technological education and research.Founded in 1861 in...
, where he continued to work whenever he was not studying. His first job was as a Teaching Assistant in Mineralogy, then as a Geologist
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...
at Cominco
Teck Cominco
Teck Resources Limited known as Teck Cominco until late 2008, is a Canadian mining company. It was formed from the amalgamation of Teck and Cominco in 2001.-History:...
, then as a Research Assistant in Geochronology
Geochronology
Geochronology is the science of determining the age of rocks, fossils, and sediments, within a certain degree of uncertainty inherent to the method used. A variety of dating methods are used by geologists to achieve this, and schemes of classification and terminology have been proposed...
. In 1964, he obtained his PhD
Doctorate
A doctorate is an academic degree or professional degree that in most countries refers to a class of degrees which qualify the holder to teach in a specific field, A doctorate is an academic degree or professional degree that in most countries refers to a class of degrees which qualify the holder...
in geochronology.
Career
Between 1964 and 1975, Krogh worked at the Carnegie Institution in Washington, D.C.Washington, D.C.
Washington, D.C., formally the District of Columbia and commonly referred to as Washington, "the District", or simply D.C., is the capital of the United States. On July 16, 1790, the United States Congress approved the creation of a permanent national capital as permitted by the U.S. Constitution....
He was a post-doctoral fellow in isotopic
Isotopic
The word isotopic has a number of different meanings, including:* In the physical sciences, to do with chemical isotopes;* In mathematics, to do with a relation called isotopy.* In geometry, isotopic refers to facet-transitivity....
geochemistry
Geochemistry
The field of geochemistry involves study of the chemical composition of the Earth and other planets, chemical processes and reactions that govern the composition of rocks, water, and soils, and the cycles of matter and energy that transport the Earth's chemical components in time and space, and...
until 1964 when he became a Scientific Staff Member. From 1964 to 1970, he specialized in Rubidium
Rubidium
Rubidium is a chemical element with the symbol Rb and atomic number 37. Rubidium is a soft, silvery-white metallic element of the alkali metal group. Its atomic mass is 85.4678. Elemental rubidium is highly reactive, with properties similar to those of other elements in group 1, such as very rapid...
–Strontium
Strontium
Strontium is a chemical element with the symbol Sr and the atomic number 38. An alkaline earth metal, strontium is a soft silver-white or yellowish metallic element that is highly reactive chemically. The metal turns yellow when exposed to air. It occurs naturally in the minerals celestine and...
dating of minerals and rocks. In 1970, he switched to specializing in the Uranium-Lead dating of zircon
Zircon
Zircon is a mineral belonging to the group of nesosilicates. Its chemical name is zirconium silicate and its corresponding chemical formula is ZrSiO4. A common empirical formula showing some of the range of substitution in zircon is 1–x4x–y...
s and other minerals.
In 1975, Krogh returned to Canada to work as the Associate Curator/Director of the Royal Ontario Museum’s Geochronology Laboratory. In 1976, he became a Professor in the Geology Department of the University of Toronto
University of Toronto
The University of Toronto is a public research university in Toronto, Ontario, Canada, situated on the grounds that surround Queen's Park. It was founded by royal charter in 1827 as King's College, the first institution of higher learning in Upper Canada...
. In 1978, he shifted to be Graduate Faculty Member with the university.
In 1979, he returned to the Royal Ontario Museum to be their Full Curator.
He worked on the Lithoprobe
Lithoprobe
Lithoprobe is a Canadian national geoscience research project funded by the Natural Sciences and Engineering Research Council. Its aim is to research and map the lithosphere structure and composition. Lithoprobe derives from "probing the lithosphere"....
project between 1991 and 1996.
Discovery
Krogh’s main focus of research has been geochronology, an effort which has long involved the integration of field work (particularly in high-grade gneisses of the Grenville Province) with clean-laboratory isotope dilution techniques. With uranium-lead (U-Pb) dating he developed a simple, yet innovative air-abrasion technique for removing exterior portions of minerals that may have suffered Pb-loss, which, combined with improved magnetic separation methods, greatly improved the accuracy and precision of zircon geochronology. In addition, Krogh's laboratory methods for the dissolution of minerals and the subsequent chemical separation of trace quantities of uranium and lead resulted in a significant reduction of environmental Pb contamination (blank) to ultra-low levels, and permitted increasingly small quantities of mineral grains and sub-grain domains to be analyzed. In the mid-1980's, he was instrumental in producing a synthetic 205Pb isotopic tracer (spike) that was distributed for use in U-Pb geochronology laboratories worldwide. The application of Krogh's novel and innovative techniques has revolutionized U-Pb geochronology and permitted the ages of rocks to be determined with unprecedented accuracy and precision. Most of what is known of the Earth’s 4.5 billion-year history has been placed in precise geological sequence using these dating methods.Honors
- 1989, awarded the Logan MedalLogan MedalThe Logan Medal is the highest award of the Geological Association of Canada. Named after Sir William Edmond Logan, noted 19th century Canadian geologist. It is presented annually to an individual for sustained distinguished achievement in Canadian earth science.-References:*...
by the Geological Association of CanadaGeological Association of CanadaThe Geological Association of Canada promotes and develops the geological sciences in Canada. The organization holds conferences, meetings and exhibitions for the discussion of geological problems and the exchange of views in matters related to geology... - 1990, made a fellow of the American Geophysical UnionAmerican Geophysical UnionThe American Geophysical Union is a nonprofit organization of geophysicists, consisting of over 50,000 members from over 135 countries. AGU's activities are focused on the organization and dissemination of scientific information in the interdisciplinary and international field of geophysics...
- 1991, bestowed an honorary D.Sc. by Queen’s University
- 1991, awarded the J. Tuzo Wilson MedalJ. Tuzo Wilson MedalThe J. Tuzo Wilson Medal is given out annually by the Canadian Geophysical Union to recognize scientists who have made an outstanding contribution to the field of geophysics in Canada. Factors taken into account in the selection process include excellence in scientific or technical research,...
by the Canadian Geophysical UnionCanadian Geophysical UnionThe Canadian Geophysical Union/Union géophysique canadienne began as a society dedicated to the scientific study of the solid earth and has evolved into one that is concerned with all aspects of the physical study of Earth and its space environment, including the Sun and solar system... - 1994, became an elected member of the Norwegian Academy of Science and LettersNorwegian Academy of Science and LettersThe Norwegian Academy of Science and Letters is a learned society based in Oslo, Norway.-History:The University of Oslo was established in 1811. The idea of a learned society in Christiania surfaced for the first time in 1841. The city of Throndhjem had no university, but had a learned...
- 1995, became a distinguished fellow of the Geological Association of Canada
- 1996, awarded the Past President’s Medal by the Mineralogical Association of Canada
- 1997, became a Geochemistry Fellow of the Geochemical SocietyGeochemical SocietyThe Geochemical Society is a nonprofit and international scientific society for the purpose of encouraging the application of chemistry to solve problems involving geology and cosmology...
and European Association of GeochemistryEuropean Association of GeochemistryThe European Association of Geochemistry is a pan-European organization founded to promotes geochemical research. The EAG organizes conferences, meetings and educational courses for geochemists in Europe, including the Goldschmidt conference which it co-sponsors with the North American Geochemical... - 1999, became an elected fellow of the Royal Society of CanadaRoyal Society of CanadaThe Royal Society of Canada , may also operate under the more descriptive name RSC: The Academies of Arts, Humanities and Sciences of Canada , is the oldest association of scientists and scholars in Canada...
Select publications
- Davis, D.W., Williams, I.S., Krogh, T.E., 2003. Historical development of zircon geochronology. In Reviews in Mineralogy and Geochemistry, J.M. Hanchar and P.W.O. Hoskin (Editors) volume 53, p.145-181.
- Krogh, T.E., Kamo, S.L., Gower, C. and Owen, J.V., 2002. Augmented and reassessed U-Pb geochronological data from the Labradorian-Grenvillian front in the Smokey archipelago, eastern Labrador. Canadian Journal of Earth Sciences 39: 831-843.
- Krogh, T.E., Kamo, S.L. and Bohor, B. 1996. Shock metamorphosed zircons with correlated U-Pb discordance and melt rocks with concordant protolith ages indicate an impact origin for the Sudbury Structure. In Earth Processes: reading the isotopic code. A. Basu and S. Hart, eds. Geophysical Monograph 95, Washington, D.C.: American Geophysical Union, pp. 343-353.
- Chen, Y. D., Krogh, T. E., Vetrin, V. R. and Mitrofanov, F. P. 1994. Precise zircon geochronology on Archean rocks sampled by the world's deepest continental borehole, SD-3 Superdeep Well, Kola Peninsula, Russia. ICOG-8 Program with Abstracts, 56..
- Krogh, T.E., Kamo, S.L., Sharpton, V., Marin, L. and Hildebrand, A.R. 1993. U-Pb ages of single shocked zircons linking distal K/T ejecta to the Chicxulub crater. Nature 366: 731-734.
- Krogh, T.E. 1988. High precision U-Pb ages of single zircons and parts of zircon in simple and complex populations. Chemical Geology 70: 70.
- Krogh, T.E. 1961. The titaniferous magnetite deposit of the Newboro District. M.Sc. Thesis, Department of Geology, Queen's University, Kingston, Ontario.
- An entry in Encyclopædia BritannicaEncyclopædia BritannicaThe Encyclopædia Britannica , published by Encyclopædia Britannica, Inc., is a general knowledge English-language encyclopaedia that is available in print, as a DVD, and on the Internet. It is written and continuously updated by about 100 full-time editors and more than 4,000 expert...
on isotopic dating.