In the Cretaceous (145–66 Ma), Laurasia split into the continents of North America and Eurasia. Sea levels rose globally during this period and much of low-lying Scotland was covered in a layer of chalk. Although large deposits of Cretaceous rocks were laid down over Scotland, these have not survived erosion except in a few places on the west coast such as Loch Aline in Morvern where they form a part of the Inner Hebrides Group. At the end of this period the Cretaceous–Palaeogene extinction event brought the age of dinosaurs to a close.