Learn how scientists determine the birthdate for our mother earth. In the beginning it was an estimated cooling rate from a flaming orb to our cooled solid exterior. Later radiometric age dating measurements of rocks in old formations and meterors began to be compared. These and other methods now converge on a common date of birth.
Mother Earth: Getting the Age out of a REAL Senior Citizen Ain’t Easy
Presenter Richard Hurst and wife Maria - click for more
Canada's Claim to Oldest Rock - The Acasta Gneiss Click for more
Meeberrie Gneiss - Australia's claim to Oldest Click for more
Oldest Meteorite Found - Click for More
Abstract of Talk
Following the Apollo 11 Lunar landing in July of 1969, a fervent interest developed in early Earth history. How old were the oldest rocks on Earth? Was Earth subjected to the scale of meteorite bombardments that were observed on the moon and if so, when did this occur? Not only did the Apollo Missions fire our scientific interests, but the technological advances in computer sciences and chemical analyses required to get information from very small lunar samples opened up totally new avenues of geologic research. My early opportunities as both a undergraduate and graduate Ph.D. allowed me to be associated with exceptional pioneering geochronologist helping form a lifelong interest in this very ancient investigation process of our planet.
At UCLA, my work began in Sudbury, Ontario, the location of the Sudbury Nickel Irruptive (SNI), which was, at the time, hotly debated as being of volcanic in origin rather than an ancient meteorite impact site (an astrobleme). Field and petrologic data collected by other researchers in the field as well as my doctoral work slowly shifted the thinking to the meteorite impact theory. Age dating that I performed indicated the impact occurred 1.85 billion years ago but was metamorphosed by the Penokean Orogeny in the Canadian Shield circa 1.7 to 1.75 billion years ago. This deformation led to the current oval shape of the SNI rather than the normal circular shape prevalent in impact craters. Then came Vic McGregor of the Greenland Geological Survey.
Circa 1972, McGregor identified very ancient metamorphic rocks in Western Greenland--their age was later determined to be 3.6 billion years old. While CalTech and Oxford scientists planned their treks to Western Greenland, back at UCLA, my advisor offered a seminar on the oldest Earth rocks. In the intervening years since this original work was undertaken the age of our planet has increased and has become clearer. Now a number of methods are used to corroborate our planet's age, now commonly agreed to.
In conclusion, my lifelong interest in Earth Science led me to investigate Earth’s earliest history. My personal experience with science, that began, in part, as a result of a potentially lethal birth defect defined my course in life. Like my research on both rocks that ranged in age from those that are very old to those that are very young, I have been fortunate as an educator to have brought Earths’ history to students of all ages---I hope to keep doing so until, I too reach an age where students confuse my age with that of the most ancient rocks on Earth.
The Presenter - Richard (Rick) Hurst Ph.D.
Richard W. Hurst received his Doctorate in PGeology and Geochemistry from the University of California, Los Angeles in 1975 after receiving his Bachelor of Science Degree in Earth and Planetary Sciences from the State University of NY at Stony Brook in 1970. Following a three year Postdoctoral position at the University of California, Santa Barbara, he joined the Faculty in the Department of Geological Sciences, California State University, Los Angeles.
He “retired” (yeah right) from CSU, Los Angeles in 2006 after 30 years of service and is now a Senior Adjunct Professor of Geology and Geochemistry at California Lutheran University. He is also the President of Hurst & Associates, Inc, his consulting firm that provides expert consulting and litigation services to geotechnical/legal/industrial clients in forensic environmental and groundwater geochemistry.
Dr. Hurst is well known for developing the ALAS Model, a geochemical technique for estimating the age of leaded gasoline releases as well as establishing the ages of very ancient metamorphic rocks in Labrador, the latter being the subject of his talk to the CGS this evening. His research activities over his life have spanned the entire realm of geologic history
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