T HE P HYSICAL L ANDSCAPE Glacial Processes, Landforms eologically, the Great Lakes ecosystem and Sediment Types MORAINES is very young and can be thought of In 1840, the famous naturalist Louis Agassiz was one of the first to as an evolutionary laboratory.” champion the concept of an ice age. From observations of the processes, – The Nature Conservancy landforms and sediments associated lacial ice results from Sometimes the rate of melting exactly “G with modern mountain glaciers, condensed snow matches the rate of ice flow, so the Agassiz concluded that massive The Lake Huron to Lake Erie Corridor’s The Ice Age period is called the Wisconsin Stage. accumulating year after glacier’s terminus becomes stationary. continental ice sheets once existed present physical landscape has been It began about 110,000 years ago year without melting. The flowing ice behind it continues For the last two million years, Earth has in Scandinavia and all of northern profoundly affected by a remarkable and ended about 10,000 years ago GWhen the ice becomes about 66 ft to bring more till, which is deposited been in an ice age, characterized by two Europe. The theory that the present is geologic event - an ice age. Long ago, when the Holocene Epoch began. (20 m) thick, it begins to slowly flow on top of the till already at the edge. alternating climatic states known as the key to the past is called actualism. glaciers more than a mile (1.6 km) thick During the peak of the Wisconsin under the force of its own weight. This creates a ridge or hill, called an glacial periods and interglacial periods. It is an important philosophical covered the entire Great Lakes Region. Stage about 20,000 years ago, ice As the ice moves, it scrapes and shears end moraine. concept used by geologists to unravel As they moved from north to south, the During glacial periods, our planet cooled. completely covered what is now the the underlying land surface. Moving Earth’s history. By mapping glacial When a glacier melts rapidly, the glaciers picked up and carried sediments Giant sheets of ice expanded and covered Great Lakes Basin. The southern like a conveyor belt, the glacier picks grooves, sediment types and terminus does not pause to build and bedrock, then deposited them to 30 percent of the land located at mid to edge, or terminus, of this ice sheet up rocks and sediments of all types landforms, geologists can reconstruct an end moraine. Rather, it deposits shape landforms throughout high latitudes in the Northern extended as far south as the Ohio and sizes, and transports them to the former extent and flow of the sheets of till that form rolling plains the region. Hemisphere. These cold, dry glacial River. lower, warmer latitudes. When the called ground moraines. periods lasted about 100,000 years. ancient continental ice sheets that edge of the glacial ice melts, it Geologists have studied these landforms For the last 10,000 years the Earth once covered the Great Lakes Basin. deposits poorly sorted sediment as well as sediment types, erosional Interglacial periods begin when Earth has been in a warm interglacial This type of study provides a link called till. features and fossils to piece together abruptly warms and the ice sheets melt. period known as the Holocene between the ice age theory originally this area’s glacial history. Their findings Warm, moist conditions allow soils to Epoch. The timing of natural described by Agassiz in Europe and reveal the crucial role that ice played in develop and life to return to the terrain. cycles suggests the Earth should the glacial history that defines the the evolution of the biodiversity that Interglacial periods are relatively brief, again be heading back to a cold landscape of southeastern Michigan exists today. typically lasting 10,000 to 15,000 years. glacial period within the next several and southwestern Ontario. thousand years. North America’s most recent glacial Glaciers Leave Tracks Glaciers create unique landforms, sediment types and erosional patterns. They also carry rocks of all sizes for great distances. Many of the glacial JOHN M. ZAWISKIE JOHN rocks found in the Lake Huron to M. ZAWISKIE JOHN Lake Erie Corridor came from the This is till beneath the lower east side A glacier in the Queen Alexandria Range Canadian Shield north of Lake of Detroit. Till is a poorly sorted sediment of Antarctica forms an end moraine. Huron. These relocated rocks are deposited by melting ice. It contains pebbles, called glacial erratics. Their surfaces cobbles and boulders set in clay or fine commonly have grooves and facets sand. Soils that developed on clay-rich till support beech-maple forests, while from being scraped under the ice. better-drained soils developed from sandy The shearing and abrasion by the till support oak-hickory forests. rock-studded ice also grooves the underlying land surface. A MODERN DAY GLACIER ictured is a modern day glacier in southwest Alaska transporting glacial erratics. Glacial erratics are large boulders carried great distances from their original bedrock source by glaciers. P JOHNSON DR. SHARON Buhr Park Children’s Wet Meadow, Ann Arbor, Michigan. 6 EXPLORE OUR NATURAL WORLD: A BIODIVERSITY ATLAS OF THE LAKE HURON TO LAKE ERIE CORRIDOR | THE PHYSICAL LANDSCAPE THE PHYSICAL LANDSCAPE | EXPLORE OUR NATURAL WORLD: A BIODIVERSITY ATLAS OF THE LAKE HURON TO LAKE ERIE CORRIDOR 7 Kettle Glacial Lakes lakeplain were eroded by the glacial lakes Sometimes a block of melting ice Large glacial lakes are created by and are not easy to identify today. detaches from the glacier and is left water that has ponded between the The cities of Mt. Clemens, Detroit and on the outwash plain where it ice front and the previously formed Windsor were built on the Detroit becomes buried by sediments. When end moraines. Sediments deposited water-lain moraine. The Leamington the ice block melts, it forms a kettle in deeper parts of glacial lakes are Moraine is only visible as a high knob depression, which often fills with typically fine-grained clay and silt. west of Leamington, melt-water or groundwater and Sand and gravel usually are deposited Ontario. Farther east, becomes a lake. Kettle lakes and in long ridges in near-shore sandbars, Ridgetown, Ontario, kames commonly are both found along beaches and in coastal dunes. was named for the USGS DIGITAL DATA SERIES DD521 DATA USGS DIGITAL on ground moraines; morainal deposits together they form As water drains from a glacial lake, on which it sits. kettle and kame it leaves a flat lakeplain with beach Aboriginal people A sandy beach ridge with wide-spreading oak ridges, channels and wave-cut and pioneers traveled trees lies parallel to the Detroit River shoreline topography. A good in Brownstown Township, Michigan. Pioneer terraces. The topography of Essex along these moraines example of this is at BRIGHAM-GRETTE DR. J. cemeteries often were built on the sandy ridges Stony Creek County, Ontario, exemplifies the because they support- left by ancient glacial lakes. flat landscape left by glacial lakes. Metropark near ed forests that were easier to traverse than (Left) Lacustrine clay and silt are sediments the surrounding swamps of the lakeplain. Rochester, Michigan. Water-lain moraines are low-lying deposited in glacial lakes. The soils that later One route used by pioneers was the formed on these deposits are poorly-drained landforms that develop where the (Above inset) A kettle lake ringed by spruce Talbot Trail, which followed a moraine and, generally, support hardwood swamp trees and permafrost patterned ground in ice meets the glacial lake. In the forests and lakeplain prairie. The low hills in the center of the photo are kames in Greenland. (INSET) NATURAL RESOURCES CANADA, TERRAIN from Essex to Ridgetown, Ontario. SCIENCES DIVISION, CANADIAN LANDSCAPES the Hudson Bay lowlands of Canada. Corridor, water-lain moraines on the Kames LANDFORMS CREATED BY GLACIERS Kames are low hills of layered sand and ENVIRONMENTS IN FRONT OF GLACIERS gravel deposited by glacial melt-water. These sediments could come from The great amount of melt-water away from the glacier. They streams that flow beneath the glacier released by glaciers can result in the deposit the sediments in well- and emerge as a delta at the ice front, formation of rivers in front of the sorted sheets of sand and gravel. or from river and lake sediments ice. These rivers carry sediments These deposits are called outwash. deposited on top of the glacier. Landforms Beneath Glaciers: Eskers Retreating Ice Sheet Stream Esker Kettle Lakes Ground BALTHAZAR KORAB BALTHAZAR Outwash Moraine Outwash is well-sorted sand and gravel deposited by braided streams. The example Ground Moraine OAKLAND COUNTY PLANNING & ECONOMIC DEVELOPMENT SERVICES COUNTY OAKLAND featured above was photographed beneath the Cranbrook Institute of Science in In some cases, long, winding rivers flow in Recessional Bloomfield Hills, Michigan. This type Moraine tunnels beneath a glacier. Sediments deposited of sediment is found in outwash plains, into these tunnels form ridges of layered sand LOWELL THOMAS kames and eskers. Outwash deposits Outwash Plan and gravel that are left behind when the evolve into extremely well-drained soils Pictured is the Exit Glacier in Alaska glacier recedes. These landforms are called which, on uplands, support oak barren, with moraine and outwash plain End Moraine eskers. The yellow highlighted portion in the woodland and prairie communities. (stream deposits.) aerial photograph above is an esker in Oakland County, Michigan. 8 EXPLORE OUR NATURAL WORLD: A BIODIVERSITY ATLAS OF THE LAKE HURON TO LAKE ERIE CORRIDOR | THE PHYSICAL LANDSCAPE THE PHYSICAL LANDSCAPE | EXPLORE OUR NATURAL WORLD: A BIODIVERSITY ATLAS OF THE LAKE HURON TO LAKE ERIE CORRIDOR 9 T HE G LACIAL H ISTORY OF THE L AKE H URON TO L AKE E RIE C ORRIDOR The Great Lakes were not always as we know them today.