Scientists have discovered fissures in tectonic plates that began to form about 18 million years ago under already shrinking ice fields. Extensive ice sheet shrinkage is thought to have driven the rapid uplift of rock layers in Patagonia.
“The variation in the size of the glaciers, as they grow and shrink, combined with the mantle structure we described in this study, is driving the rapid increase and spatial variables in this region,” said geophysicist Hannah Mark of the Woods Hole Oceanographic Institution. Tuesday (1/3/2022).
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Hannah Mark, who led the study, explained that when a glacier melts, the layer of earth beneath it bounces and rises, because it is no longer burdened by miles of thick ice. This increase, called glacial isostatic adjustment, usually occurs over thousands of years.
However, the phenomenon that occurs in Patagonia this rise occurs in decades, so it is faster than the speed it should be. The rapid removal of the layer results in an increase of more than 4 centimeters per year.
In this study, Mark and colleagues recorded seismic data around the Patagonia ice fields straddling the Andes Mountains in southern Chile and Argentina. The goal is to map what’s going on beneath the surface.
Read also; Ice Sheet Thinning, Temperature in Antarctica Rises 1.8 Degree Celsius
These 10-month measurements, combined with other seismic data from local monitoring stations. The results reveal how fissures in the tectonic plate nearly 100 kilometers beneath Patagonia have allowed hotter mantle material to flow beneath the continent.
This lower-than-usual viscosity in the mantle beneath this Patagonian ice field could accelerate continental uplift, associated with ice melt. “This explains why GPS measures the large lift due to loss of ice mass [di Patagonia],” said seismologist Douglas Wiens of Washington University in St. Louis.
(wib)
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