Geologists have traditionally believed that Earth’s crust comes in two distinct types. Oceanic crust, which covers nearly two-thirds of Earth’s surface, is found beneath the deep ocean. It is, on average, four miles thick and is made of basalt, a dense igneous rock formed from lava. Continental crust makes up the continents and their margins. It is about twenty to thirty miles thick and more complex in composition, though dominated by granite.
In 2021 a team of Earth scientists based in Europe published their hypothesis that the North Atlantic Ocean may hide a vast region of a new kind of sunken continental crust. Their work is an attempt to explain the geology of Iceland, a volcanic island in the North Atlantic. The crust under Iceland is known to be twenty-five miles thick, which is much thicker than typical oceanic crust.
The surprising result of their research is that Iceland may be just the ‘tip of the iceberg’ of a broad area of quasi-continental crust. On the basis of several lines of evidence, the researchers propose that the region of sunken continental crust may extend from England all the way to Greenland, and cover about three hundred eighty thousand square miles. They call the posited sunken continent ‘Icelandia’. It is one of several areas within the world’s oceans where sunken areas of continental crust may exist.
If the sunken continent does exist, the discovery could have important economic ramifications, because continental crust can contain valuable mineral and hydrocarbon deposits, with their ownership uncertain under current international law. The researchers hope to test their controversial hypothesis by undersea drilling, and by studying how seismic waves travel through the North Atlantic crust.