Historical Geomorphology of the Great Lakes Region

By: Foster Valle

Natural Resources Management

State University of New York- College of Environmental Science and Forestry

To understand current natural systems, it is crucial to know the factors that contributed to the formation of geomorphological features that we witness today. Geomorphology is the study of landforms and their evolution through physical, chemical, and biological processes. Topographic features such as hills, lakes, mountains, lakes, and rivers are dynamically formed over time, leaving evidence of their formation and seemingly permanent presence in the current landscape. The Great Lakes are an exceptional hydrologic phenomenon that holds great importance -- not only for the region, but for the whole country. Holding 85% of North America's fresh surface water and 20% of the world’s, these lakes are integral in understanding how we manage fresh water which is an ever depleting natural resource (Allen, 1975). The five lakes including Lake Superior, Lake Michigan, Lake Huron, Lake Erie, and Lake Ontario are interconnected, creating unique regional hydrologic patterns, which are potential gateways for invasive species to spread and a shared interest in ensuring water quality among the entire Great Lakes watershed. Four of the five Great Lakes are located between the United States and Canada; because of this, not only do the lakes create natural boundaries, but also serve as a cultural center.

Beginning approximately 2.6 million years ago, Pleistocene glaciation started to shape the topography of the Great Lakes region; with multiple advances of continental glaciers from the North, powerful forces eroded the Silurian-age bedrock, producing terminal moraines (Bornhorst, 2016). Terminal moraines are ridges that mark the maximum size of glaciers or distance glaciers advanced, and are composed of  the sediment that was initially moved and trapped by the glacier's. This process helped form the unique geologic composition of sand, silts, clay, gravel and topography that we see in the Great Lakes region today. As the glaciers retreated, the melted water flowed to topographic depressions and lakes were formed by terminal moraines damming water.The sediment that was initially moved and trapped by the glaciers fell out and deposited at the basin of the newly formed lakes (Bornhorst, 2016).

The Wisconsin Glacial Episode, occurring  150,000 years ago, was the most recent glacial movement that affected the topography of the Great Lakes. The glacier followed what was referred to as  the Ontarian River Valley and left behind the characteristic abundance of sands and gravel that can be seen throughout the region and on our shorelines (Allen, 1975). Although this valley no longer exists as a valley, it was oriented in the same direction as Lake Ontario and guided the glacier’s path. It aided in the formation of a temporary lake, called Lake Iroquois, that was bigger than the current Lake Ontario. Lake Iroquois shrank to the current size of Lake Ontario when the surrounding land gradually rebounded from the immense weight of the glacier that had covered it for thousands of years. Glaciers carved various topographic features that we are familiar with today. Although the formation of the Great Lakes region occurred thousands of years ago, understanding how the various topographic features that we are familiar with today were formed remains important for future conservation and preservation of the  region.

References:

• Allen, W.B., Waller, R.M., Great Lakes Basin Framework Study: Appendix 3-- Geology and Ground Water: Great Lakes Basin Commission, Ann Arbor; Appendix 3 of Great Lakes Basin Framework Study, 1975. 152 p. 60 Fig, 15 Tab, 76 Ref.

•  Bornhorst, T.J. (n.d.). AN OVERVIEW OF THE GEOLOGY O THE GREAT LAKES BASIN. In Museum Mtu. Retrieved from https://museum.mtu.edu/sites/default/files/2019-11/AESMM_Web_Pub_1_Great_Lakes_Geology_0.pdf