The Devonian Period coast of North America was located farther towards the craton than it is today. During this time, a broad carbonate shelf covered most of the western interior, including Nevada, with several deeper basins located all around the submerged part of the continent. Present day Nevada was located near the western margin of the North America, and was entirely covered by water. In this area there was a break in slope where flat lying shelf bathymetry began to deepen at an angle of a few degrees. This is known as the continental slope which, like the shoreline, was located farther inland during the Devonian Period. Since that time, tectonic forces and global fluctuations in sea level have exposed the rocks deposited in these regions, allowing geologists to reconstruct how the planet once looked.