During the Carboniferous period (363-290 Ma), Scotland lay close to the equator. Several changes in sea level occurred during this time. The coal deposits of Lanarkshire, and further sedimentary deposits, date from this time. More volcanic activity formed Arthur's Seat in Edinburgh, among other hills. By the Triassic, Scotland was a desert, the origin of large sandstone outcrops of the southwest. Although large deposits of Cretaceous rocks would have been laid down over Scotland, these have not survived erosion, as have the chalks of England.