Plate Tectonics and People

G. Brent Dalrymple

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Dr. Dalrymple, Dean, College of Oceanic and Atmospheric Sciences, Oregon State University.  Image Source:


Biographical Information

Geologist Gary Brent Dalrymple was born in Alhambra, California on May 9, 1937 and raised in Bell, California.  Currently residing in Corvallis, Oregon, he is the son of a bricklayer and dedicated hunter.  Dalrymple's interests as a youth included basketball, tennis, and hunting.  Learning the trade of a bricklayer from his father, he was admitted into the bricklayers union as a journeyman around the age of 16.  Upon graduating from Bell High School in mid-winter, Dalrymple worked for various contractors while taking classes at the local community college.  When it came time to transfer, he applied to three colleges, Cal Tech, MIT, and Occidental.  Although he did not gain admission into Cal Tech, he was accepted by both MIT and Occidental, choosing the latter for its proximity to home.  Dalrymple notes, "It was a good choice for many reasons.  Among them, Oxy is where I met Sharon and we've been married since graduation."

Dalrymple entered Occidental as a physics major thinking he might like to go into physics or possibly engineering.  Luckily, he was required to take a beginning geology course with, "then chair of the 2-person geology department", Joseph Birman.  Inspired by Birman's lectures, and intrigued by "this unfamiliar science", Dalrymple requested an appointment with his professor to discuss the possibility of majoring in geology.  "We spent a bit of time talking about all of the things that were not understood about the Earth--discoveries just waiting to be made.  I was hooked and switched majors immediately.  I've never been sorry."

Graduating from Occidental College with his B.A. in Geology in 1959, Dalrymple headed off to U.C. Berkeley to pursue his Ph.D., also in Geology.  During the summer of 1962, while on a United States Geological Survey (USGS)-organized field trip, Dalrymple met USGS scientists Allan Cox and Richard Doell, both graduates of Berkeley.  "Allan drew me aside one evening to talk...around a campfire...about the ancient magnetic field--he and Dick were pioneers in paleomagnetism and had already established considerable reputations."  It was Dalrymple's knowledge of radiometric dating that piqued Cox's and Doell's interest; and from that field trip, his recruitment into the USGS began.

Upon the completion of his Ph.D. in 1963, Dalrymple was immediately hired by Cox and Doell to join in on the task of deciphering the history of the Earth's magnetic field.  The work by the trio would earn Cox and Doell the prestigous Vetlesen prize in 1971 (Dalrymple was apparently too young).  Dalrymple spent the next 31 years (1963-1994) of his brilliant career with the USGS, later becoming Assistant Chief Geologist for the Western Region.  In addition to his research during his tenure with the USGS, Dalrymple joined the American Geophysical Union (AGU) in 1963, became a Fellow in 1975, designated President, Section of Volcanology, Geochemistry, and Petrology, in 1984, and then resided as President of the AGU from 1990-1992.  He is a member of both the American Academy of Arts & Sciences and the National Academy of Sciences, inducted 1992 and 1993, respectfully; and in 1993, thirty-four years after receiving his Bachelor’s Degree, Occidental College awarded Dalrymple an Honorary Doctorate for his outstanding achievements.

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Dr. Dalrymple, AGU President.  Image Source:


In 1994, Dalrymple was offered, and accepted, the position of Dean of the College of Oceanic and Atmospheric Sciences at Oregon State University (OSU) in Corvallis, Oregon, thereby retiring from the USGS, adding that “it was a chance to do something else.”  Initiating a piece of advice given by a retired colleague, Dalrymple stepped aside as dean in 2001 in order to let "...the young people do the really important science and...get out of the way and leave the money and space to younger people."  Dalrymple and his wife, Sharon, continue to call the Corvallis area their home.  In addition to golfing, skiing, woodworking, and flying airplanes, Dalrymple is "...generally enjoying life".


Specific contributions to plate tectonic theory / solid Earth geophysics

Upon his hiring by Allan Cox and Richard Doell of the USGS in 1963, Dalrymple's first mission was to construct, from scratch, a state-of-the-art lab in order to begin his work on radiometrically dating rock specimens collected from the ocean.  In a 2005 issue of Geotimes, Dalrymple elaborated on the challenge of the technology at the time (1963):  “You couldn’t buy mass spectrometers that were nearly sensitive or clean enough to do that kind of couldn’t even buy a high voltage power supply…now you can buy those things off the shelf”.  By late 1965, the team of Dalrymple, Cox, and Doell had successfully created the first geomagnetic polarity timescale for the past 3.5 million years.

According to Dalrymple, it was known at the time that volcanic rocks became magnetized in the direction of the ambient magnetic field when they cooled.  Since the Earth's magnetic field is global, if one knows the direction of the field at one place, then one can approximate the positions of the poles.  Furthermore, it was also known that many volcanic rocks were magnetized in a direction opposite to that of Earth's present field, but whether it was due to a reversed magnetic field or to some property of the rocks that caused them to be reversely magnetized was not known.  "A simple experiment that could solve this problem was to measure the ages and magnetic directions of a sufficient number of volcanic rocks from several geographic areas and plot Earth's magnetism (normal or reversed) against time.  If normal and reversed rocks fell into distinct time periods, then it had to be due to reversals of the field.  If the plot was randomly scattered, then it had to be some property of the rock causing the reverse magnetism."

Cox and Doell, pioneers in paleomagnetism at the time, could measure the magnetic direction of the rock, but not the ages.  Enter Dalrymple.  "I could measure ages using long-lived radioactive isotopes--specifically using the K-Ar method--a relatively new field at the time that I had learned from professors Garniss Curtis, Jack Everenden, and John Reynolds."  It is for this reason that Cox and Doell hired Dalrymple.  "We were successful and it ended up being even more important than we initially thought...and had no idea at the time our research would play an important part in a theory that would revolutionize earth science." 

The significance of their research was realized when Frederick Vine and Drummond Mathews matched Dalrymple's geomagnetic timescale to the magnetic stripes located on the ocean floor.  Vine and Mathews had proposed just three years prior to the creation of the timescale that the magnetic stripes were a result of magma generated at mid-ocean ridges during times of normal and reversed magnetism.  It was Dalrymple's timescale that not only provided meaning to the stripes, but also showed that the ages of seafloor rocks increased with increasing distance from mid-ocean ridges; thereby, supporting both the Vine-Mathews hypothesis and Harry Hess's hypothesis of seafloor spreading.  The combined work of Dalrymple and many others greatly contributed to the development of the theory of plate tectonics.

In 2003, Dalrymple earned America's most prestigious scientific award, the National Medal of Science, “For his pioneering work in determining the geomagnetic polarity reversal timescale; a discovery that led to the theory of plate tectonics.”  The following excerpt is from an interview with Dr. Dalrymple found on Occidental College's News & Events page (March 1, 2005):

“It’s a nice recognition,” Dalrymple said from his home in Corvallis, Ore. “What we did is sometimes called the Rosetta stone of plate tectonics. These kinds of scientific revolutions don’t happen very often. In terms of importance to science, it was similar to what physics did around the turn of the century with the discovery of subatomic particles and how the atom worked, and the discovery of DNA in the ‘60s. It was a very similar kind of revolution.”

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Left Image:  National Medal of Science.  Image Source:                                            Right Image:  Dr. Dalrymple receiving the National Medal of Science from President Bush in 2005.  Image Source:

Other interesting scientific contributions

Besides his contribution to the development of the theory of plate tectonics, Brent Dalrymple is probably best known for his work on the age and evolution of the Hawaiian-Emperor volcanic chain.  Sampling all of the volcanic islands and many of the seamounts in the chain, Dalrymple, Dale Jackson, and David Clague (along with contributions from many other colleagues), showed that the volcanoes are all similar in type and increase in age systematically to the west and north until the chain disappears into the Aleutian Trench.

In 1981, Dalrymple served as a key witness in the McLean v. Arkansas Board of Education trial ("Creationism Trial").  The Balanced Treatment for Creation-Science and Evolution-Science Act (Act 590) mandated that equal time be given for the teaching of both evolution and creation-science.  Dalrymple testified that the creationists’ "scientific" claims were, in fact, not supported by scientific evidence.  Furthermore, Dalrymple testified to the fact that the creationists were not only irresponsibly selective with their supporting evidence, but that they nearly always failed to properly and responsibly demonstrate the scientific method.  In summary, he claimed that the ways in which the creationists practiced science did not reflect the scientific community's standards.  Ultimately, Dalrymple testified for science.

**Click the following link to read the transcripts from Dalrymple's testimony (he provides an excellent explanation on the methods used for radiometric dating and the checks and balances used in order to ensure accurate measurements.  In addition, he provides his expert insight into the scientific method and the distinction between hypotheses and theories). **

When asked about his work on the early impact history of the moon, on June 5, 2012 Dr. Dalrymple responded with the following:

"The work on the early impact history of the Moon came about because I attended a talk by Graham Ryder (Lunar and Planetary Institute) about melt rocks.  These are tiny fragments of rocks that were completely melted and recrystallized by the impacts of large bodies into the Moon early in its history.  Uncontaminated melt rocks are very tiny but are a “new” rock.  Graham thought that their ages would indicate the ages of the basin-forming impacts.  I approached Graham after his talk and told him that I thought we could measure the ages of his melt rocks.  At the time, I had just completed construction of a laser system coupled with a very sensitive mass spectrometer that was designed to measure the ages of very tiny specimens. (Derek York of the University of Toronto developed the first one of these laser systems—mine was the second in the world)  I was pretty confident that we could measure the ages of lunar samples of .005 grams or less.  What Graham and I found was that there do not seem to be any basins older than about 3.86 billion years.  The conventional wisdom of a heavy bombardment of the Moon starting at 4.5 billion years and gradually tapering off then ending with a “terminal lunar cataclysm” at 3.8 billion years seems not to be so.  Instead, it appears from our work on melt rocks that there was no early heavy bombardment after accretion but only an episode of intense bombardment around 3.8 billion years ago."


Other cool stuff you should know

At the age of 7, Dalrymple's uncle provided him with his first flight experience; and with it, a passion for it that lasts to this day.  Receiving his private pilot's license in 1956 as a freshman in college, Dalrymple flew for another 3-4 years before marriage, graduate school, children, career, and therefore, a lack of time and money, led to a halt in his flight plans.  Forty-five years later, upon retiring from OSU in 2001, Dalrymple joined the Oregon State Flying Club, got a new medical, passed a rather lengthy FAA biennial flight review, and started flying again at the age of 67.  "At 70 I got an instrument rating so Sharon and I could get up and down through the clouds.  I am still flying and will probably continue as long as I am healthy." 

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Dalrymple on a flight to the S.F. Bay Area in 2010 to visit friends and family.  Flying east or south of his home town of Corvallis requires climbing to at least 11,000 feet.  The use of oxygen at this altitude prevents fatigue.  Image source:


In addition to authoring/contributing to/reviewing hundreds of scientific papers, Dalrymple has published two books on the age of the Earth:  The Age of the Earth (1994), and Ancient Earth, Ancient Skies: The Age of Earth and Its Cosmic Surroundings (2004). 



Air Facts, the journal for personal air travel--by pilots, for pilots.  (2012).  Brent Dalrymple Bio.  Retrieved May 22, 2012 from,

American Geophysical Union. (2012).  Past President Biographies: 1980-2000.  Retrieved May 23, 2012 from,

Dalrymple, G. Brent.  Personal communication with full permission of inclusion.  From May 25, 2012 to June 10, 2012.

Geotimes.  (April, 2005).  G. Brent Dalrymple: Deep time in a tarpaper shack.  Retrieved May 23, 2012 from,

McLean v. Arkansas Documentation Project.  (December, 1981).  Testimony of Dr. G. Brent Dalrymple, U.S. Geological Survey, Menlo Park, CA (Plaintiffs Witness) - transcript paragraph formatted version.  Retrieved May 28, 2012 from,

Hough, Susan, "Plate Tectonics Revolution", excerpted from Earthshaking Science: What we know (and don't know) about earthquakes, Princeton University Press, 2002, pp. 1-12.

Occidental College, News and Events.  (March 1, 2005).  G. Brent Dalrymple '59 Receives National Medal of Science.  Retrieved May 30, 2012 from,

Oregon State University, College of Earth, Ocean, and Atmospheric Sciences.  Retrieved May 28, 2012 from,

USGS Newsroom.  (3/15/2012).  USGS Retiree Awarded Presidential Medal of Science.  Retrieved June 2, 2012 from,

Wikipedia, the free encyclopedia. (5/8/2012).  Brent Dalrymple.  Retrieved May 22, 2012 from,

Wikipedia, the free encyclopedia. (9/20/2011).  Richard Doell.  Retrieved May 22, 2012 from,

Wikipedia, the free encyclopedia. (5/21/2012).  Allen Cox.  Retrieved May 22, 2012 from,