Washington: A new study has shed light on why Greenland is covered in ice and has suggested that the ice on Greenland could only form due to processes in the deep Earth interior.
The study suggested that large-scale glaciations in the Arctic only began about 2.7 million years ago and before that, the northern hemisphere was largely free of ice for more than 500 million years.
Conditions for the glaciations of Greenland only developed so recently on a geological time scale because of the interaction of three tectonic processes i.e. Greenland had to be lifted up, such that the mountain peaks reached into sufficiently cold altitudes of the atmosphere. Secondly, Greenland needed to move sufficiently far northward, which led to reduced solar irradiation in winter. Thirdly, a shift of the Earth axis caused Greenland to move even further northward.
The authors found hints in rock samples that the high mountains in the east of Greenland were only uplifted during the last ten million years, whereby this process happened especially fast since about 5 million years ago. At that time, Greenland was still largely free of ice . Seismological investigations indicate that hot rocks rise underneath Iceland from the Earth's deep mantle.
The seismological investigations also showed that the lithosphere in the East of Greenland is especially thin only about 90 kilometers thick. Earth scientists Steinberger and colleagues reconstructed the position of the tectonic plates 60 to 30 million years ago, and found that the Iceland plume was exactly beneath this part of Greenland during that time. This explains why the lithosphere is so thin and for that reason, the eastern part of Greenland could also be more easily uplifted.
