Topography and climate A coastal plain stretched into what is now the Atlantic; to the west lay the Appalachians and the eastern Allegheny Plateau. At the era’s onset, glaciers sometimes covered even the highest peaks, except for what’s now Delaware and lower Pennsylvania. Over the period, the weather warmed, except for a brief retreat to cold between 10,800 and 10,200 years ago. The ice melted; lakes formed and the sea rose.
Plant and animal life Deer, bear, and other animals lived with caribou, mastodons, and other species that are now extinct or have since moved north. With the waning cold, forests and grasslands took root on ice-free land. next >>