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Mon April 22, 2013
Dr. Stuart Thomson, University of Arizona – The Formation of Antarctica
In today’s Academic Minute, Dr. Stuart Thomson of the University of Arizona explains the formation of Antarctica’s most dramatic and inaccessible features.
Stuart Thomson is a research scientist in the Department of Geosciences at the University of Arizona. His research involves the use and development of geochronometers and thermochronometers to determine the time and temperature history of rocks and minerals. His most recent project applied these techniques to determine the age of Antarctica’s subglacial fjords. He holds a Ph.D. from University College London.
Dr. Stuart Thomson – The Formation of Antarctica
Ice, in places over two-miles-thick, almost completely blankets the frozen continent of Antarctica. Radar surveys have peered through this ice revealing a remarkable hidden landscape. This includes mysterious entombed mountains larger than the European Alps and huge fjords twice as deep as the Grand Canyon. But radar tells us nothing about when these features formed.
Usually geologists like myself explore the landscape and carry rocks back to the lab for analysis. That’s impossible in Antarctica because the landscape is inaccessible. To tackle this problem my colleagues and I use sand drilled from the sea-bed off the coast of Antarctica. This sand is supplied by glaciers and rivers that eroded the continent’s interior and holds the key to figuring out when Antarctica’s mountains and fjords formed.
Rocks deep in the Earth cool as erosion peels away the layers of rock above. We measured this cooling in more than two-thousand sand grains using several different analytical techniques. This lets us say something about how Antarctica’s landscape has eroded over the many tens of millions of years during which sand was deposited offshore.
River sands from just before the first glaciation of Antarctica 34 million years ago reveal a slowly eroding continent at that time, indicating a rolling landscape dominated by large rivers and ancient 200 million-year-old mountains. But in sediment deposited after ice started flowing on Antarctica we discovered a record of much faster erosion; one that could only have been brought about by large glaciers carving deep fjords.
Our new findings show how glaciers have caused enormous change to Antarctica’s hidden landscape. This will help other researchers better replicate how ice formed and flowed over this landscape during the continent’s past, as well as predict how Antarctica’s ice will react to future climate change.