A enormous granite bodyabout 100 km wide, 7 km thick and dating back to 175 million years ago was discovered in West Antarcticaunder the Pine Island Glacier. The discovery was made by a team of researchers from British Antarctic Survey (BAS) and was published in the journal Communications Earth & Environment. The presence of this “granite giant” was revealed by the erratic boulders present on the surface and the aerial gravity measurements. In West Antarctica the Ice melting is particularly rapid and contributes significantly tosea level rise. Knowing what lies under the Antarctic ice is very difficult but fundamental because the subsurface geology significantly influences the dynamics of the ice on the ice sheet, in particular the rhythm with which it slides towards the sea.
How the “granite giant” buried under the ice of Antarctica was discovered
The bedrock that lies beneath the ice sheet of the Antarctic ice sheet is little known because it is difficult to reach. However, on the surface we find evidence of this in the form of erratic boulders. These rocky masses have been over time torn from the ice to the substrate on which they flowed, transported even over long distances and then deposited during the retreating phases of the cap.
The research of the British Antarctic Survey focused on the boulders distributed over theHudson Ridgea mountain range in West Antarctica. The pink granite of which they are made has been dated using the radioactive decay of elements contained in its minerals: it was thus discovered that these rocks were formed approximately 175 million years agoduring the Jurassic period. The origin of the boulders has long remained a mystery, since their composition is different from that of the volcanic rocks outcropping on the Hudson Ridge. To resolve this, field observations were supplemented with aerial gravity measurementswhich identify the variations in density of the rocks beneath the ice and therefore their lithology and distribution. These measurements revealed the presence of a huge buried granite body (about 100 km wide and about 7 km thick) beneath the Pine Island Glacier, which flows along the Hudson Ridge. The glacier, thanks to its enormous erosive force, tore large boulders from this body, then transported them and deposited them on the mountains upon its retreat. Their deposition dates back to when the ice sheet retreated at the end of the Last Glacial Maximum (Last Glacial Maximum), the period of time between 25,000 and 19,000 years ago which represents the coldest phase of the Last Ice Age.
What is the purpose of knowing Antarctica’s bedrock and why is it important
Discovery is important because it reveals how the Pine Island Glacier behaved during the Last Ice Age. Understanding this allows us to refine computer models of the ice sheet, which are essential for predict how Antarctica will respond to future climate change and how sea levels will rise. In West Antarctica the melting speed of the ice cap is currently very high: sul rate at which the ice slides towards the sea the geology of the subsoil also has an impact. This means that future research will have to focus more on erratic bouldersa precious source of information that has so far been underestimated. Since these have undergone long transport, it will always be necessary to match to understand their exact origin geophysical investigations capable of revealing buried structures.
