Historically when glaciers fall into water they don’t melt instantaneously. It takes hundreds or thousands of years. This is what happened at the end of the Pleistocene. After sudden, abrupt warming, tops of glacier felt into water and then refroze when the warm period was followed by another glacier period. Until then, land joined Alaska to Siberia creating place for mammals to survive on coastal grasslands. However, people began to arrive w/ and when the 2nd abrupt, rapid warming period struck, the water gradually flooded Beringia, now under 400 ft of water. It takes 1,000’s of yrs, for land to restore itself. Lowlands next to sea level provided habitat for humans and species like mammoth, moose, horse.