Greenland on the move
100 million years ago, Greenland was on the move. On its tectonic plate, it traveled from a more southern location northward to its current Arctic position, and along the way passed over a mantle plume or hotspot that left a record of its journey in Greenland’s rocks. A plume is an upwelling of hot rock, or magma, from hundreds of miles below Earth’s surface. When the magma reaches the base of Earth’s outer layer, which includes the crust that makes up the sea floor and continents, it heats up the rock above, effectively cooking it and altering its chemistry. For magnetic rocks common in Earth crust, heating causes them to lose their magnetism. NASA researchers used the altered chemistry of these magnetic rocks to create a heat map of Greenland, where they found the “scar” of its millennia-long journey over the hotspot. The scar extends from the northwest region to the southeast region of Greenland. Because the northwest region of Greenland moved off the plume earlier it is significantly cooler than the southeast. Tracking the movements of land masses helps scientists understand their evolution through time. But more immediately, the heat information feeds sea-level-change models on Earth by helping scientists predict the behavior of the massive ice sheet that covers Greenland.