What Was Maryland Like 20,000 Years Ago?

Twenty thousand years ago Maryland’s landscape was very different. The climate was much colder - the Chesapeake Bay did not exist. There were no people, and mammoths, mastodons, bison, and giant beavers roamed a landscape dominated by coniferous woods and marshy tundra.

This was the Ice Age: the most recent glacial episode in North America, when extensive ice sheets covered much of North American and Europe. At the time of this Wisconsin Glaciation, ice up to one mile thick covered the land as far south as northern Pennsylvania, reaching its maximum extent between 18,000 and 20,000 years BP (Before the Present). Maryland itself was not covered by glacial ice, but its climate was highly influenced by the glaciers to the north.

This glacial episode is also responsible for the formation of large portions of Maryland’s landscape. As the ice-sheets retreated, meltwaters flushed down the rivers of the ancestral Chesapeake and carved new channels across the coastal plain. These rivers carried stone rubble and sediment scraped up by the glaciers and deposited this material in layers across a vast area. The Chesapeake Bay as we know it first began to emerge about 12,000 years ago, formed when a widely branching network of river channels joined to a single tidal river flowing along the Atlantic continental shelf.

In western portions of Maryland, higher elevations brought colder temperatures and a landscape reminiscent of more northern climates.

Twenty thousand years ago, the flora and fauna of Maryland were very different. Because of colder, harsher climatic conditions, forests were dominated by cold-adapted species like spruce, fir, and pine, and the piedmont and mountain regions of the state had areas of tundra-like marshlands similar to those we know from Siberia, Alaska, and northern Canada. Prior to the glacial retreat, our familiar white-tailed deer, black bear, and beaver coexisted with now-extinct megafauna.

During the period between 20,000 and 12,000 years ago, large-scale, massive climatic changes transformed Maryland’s environment. The greatest factors in shaping the environment during this time were the indirect effects of melting glacial ice caused by a gradual global warming trend.

Further Information:

Curtin, Philip D., Grace S. Brush, and George W. Fisher
2001   Discovering the Chesapeake. The History of an Ecosystem. The Johns Hopkins University Press, Baltimore.

Flannery, Tim
2001   The Eternal Frontier. An Ecological History of North America and its Peoples. Atlantic Monthly Press, New
           York.

Grumet, Robert S.
2000   Bay, Plain, and Piedmont: A Landscape History of the Chesapeake Heartland from 1.3 Billion Years Ago to
           2000. The Chesapeake Bay Heritage Context Project. U.S. Department of the Interior, National Park Service,
           Annapolis, Maryland.

Jones, K. Bruce, Kurt H. Ritters, James D. Wickham, Rober D. Tankersley, Robert O’neill, Deborah J. Chaloud, Elizabeth R. Smith, and Anne C. Neale.
1997   An Ecological Assessment of the United States Mid-Atlantic Region. United States Environmental Protection
           Agency, Washington D.C.

White, Christopher and Karen Teramura
1989   Chesapeake Bay: A Field Guide. Tidewater Publishers, Cambridge, Maryland.