The forests of North America have seen plenty of change in a pretty short period of time, at least geologically speaking. Up until about 18,000 years ago, the Laurentide Ice Sheet covered Canada and much of the eastern United States. When temperatures climbed and the ice sheet retreated, forests gradually reemerged. But how? Did pockets of trees find refuge in sheltered areas during the Ice Age? Or were all tree species pushed to the southern tier of the United States, only to spread north again after the ice disappeared? Scientists still debate the topic, but one thing is clear: today’s forests in the eastern United States bear little resemblance to post-glacial forests. Starting with European colonial settlers and marching through four centuries of development, drought, and fire, the tree cover of North America became fragmented.
This page is part of NASA's Earth Observatory website. It features text ...
This page is part of NASA's Earth Observatory website. It features text and a scientific illustration to describe how the ocean interacts with the atmosphere, physically exchanging heat, water, and momentum. It also includes links to related data sets, other ocean fact sheets, and relevant satellite missions.