Dark volcanic peaks of Hudson Mountains in West Antarctica have shown the existence of a massive buried granite body (nearly 100 km across and 7km thick, nearly half the size of Wales in the UK) underneath Pine Island Glacier. Oddly shaped boulders that are so high in the mountains are the baffle of scientists. So, where were they found, what information would they tell of the past and future of the ice cover?
Discovery and Geological Dating of the Granite
A group of scientists, headed by British Antarctic Survey (BAS), dated the granites, by measuring the radioactive decay of elements trapped in microscopic crystals, they found that the rocks are approximately 175 million years old and dated the Jurassic era. The question of how the boulders were deposited in these mountains used to be a mystery until a new evidence was acquired through airborne surveys. The article appears in the journal Communications Earth and Environment.
Airborne Surveys and Gravity Measurements
Accurate measurements of gravity recorded by the BAS Twin Otter and other aircraft that flew over the area, indicated a strange geologic signal beneath the glacier, which was similar to the signal that a buried granite should have given.
Breakthrough: Linking Surface Boulders to Hidden Granite
The interconnection of these scattered boulders with this hidden giant granite has been a breakthrough. It does not only provide solution to an old geological riddle but provides crucial leads on the behaviour of Pine Island Glacier in the past, gouging rocks off the bottom and dropping them onto the mountains when the ice cover was so thick.
Knowledge of the ice thickness and flow regimes in the previous ice age (c. 20 thousand years ago) assists investigators in improving the computer simulations of ice sheets which are essential in forecasting how Antarctica will react to an increase in global warming.
Scientific Analysis and Interpretation
Dr. The data on the airborne survey were analyzed by Tom Jordan, the lead author and a geophysicist at BAS. It is extraordinary, it is wonderful, said he, that pink granite boulders have been noticed on the surface, and have brought us to a concealed giant under the ice. Combining geological dating with gravity survey gave us not only an enigma to the origin of these rocks, but also uncovered the fact that the ice sheet moved in a certain way in the past and may also change in the future.
The discovery also illuminates the current processes. Under Pine Island Glacier, where ice loss has been among the most active in the past few decades in Antarctica, the geology acts strongly on the movement of ice along the underlying surface, and the drainage of the melt water underneath. The new discoveries will serve in the enhancement of the computer simulations of ice flow that is applied to project the rise in sea level.
Fieldwork and Geological Evidence
The rocks collected by Dr. Joanne Johnson, one of the co-authors of the study, who was a geologist at BAS, were gathered during the fieldwork around the Hudson Mountains as part of the International Thwaites Glacier Collaboration. She says, rocks give a fantastic account of how our planet has evolved throughout the years, particularly, ice has melted and transformed the topography of Antarctica. Such boulders are a treasure trove of data regarding what is far down below the ice cover and is out of reach.
Implications for the Future of the Ice Sheet
By discovering their origin, we have been able to reconstruct their route to get where they are today, and this has provided us with some insight into how the West Antarctic Ice Sheet will be altered in the future, which is essential in calculating how sea level rise will alter the populations in the world coastlines.
Scientific Significance of the Study
This paper underlines the role of integrating various threads of science, in this instance, geology and geophysics to introduce fresh knowledge on the secrets surrounding how our planet was formed.