Large Lake Essay

The areas along the river are mainly forested; much of the area is a flat, gently rolling plain. The upland prairies were created during an intensive warming period several thousand years after the melting of the glaciers. The Illinois River Valley in the Starved Rock area is a major

The present configuration of the Great Lakes basin is the result of the movement of massive glaciers through the mid-continent, a process that began about one million years ago. . . . Studies in the Lake Superior region indicate that a river system and valleys formed by water erosion existed before the Ice Age. The Glaciers undoubtedly scoured these valleys, widening and deepening the and radically changing the drainage of the area (Encyclopedia Britannica )

During the Pinedale glaciation, there were two ice sheets. One of them being the Cordilleran Ice Sheet. The Cordilleran Ice Sheet was comprised of three main lobes. The Puget Lobe, Okanogan Lobe, and the Purcell Trench Lobe. The one lobe in Northern Idaho, near present day Lake Pend Oreille, was the Purcell Trench Lobe. When these sheets of glacial ice moved south they caused an ice dam to occur. J.T. Pardee states that “The evidence of icebergs, together with the apparent regency of the lake and the variable height of its surface, connect this lake with the glacial period, and readily lend themselves to the suggestion that its dam was of ice” (Pardee, 1910) This ice dam blocked the Clark Fork River which is near the boundary of Idaho and Montana. The water from the river was blocked and began to build up and formed Glacial Lake Missoula. Water

The processes of water erosion that were listed above are also main contributors to the elevation levels of Michigan.

Champaign County was first covered by the Illinois Glacier (191,000—130,000 years ago), which leveled the region and covered it in a deposit of boulder clay. The county’s topography was then formed by the Wisconsin Glacier about 20,000 years ago. As lobes of ice from what is now Lake Michigan crossed the county, a deep (up to 300 ft) pile of glacial soil was created and topped by numerous moraines (any glacially formed accumulations of unconsolidated debris) forming small, flat watersheds with no outlets. The moraines formed as the Wisconsin Glacier advanced and receded many times over the Midwest. The Champaign moraine system now crosses the county in a northwest-southeast direction, and between the moraines ridges are broad plains of what used to be swampy land, most of which has since been artificially drained.

Lake deposits are primarily fine-grained clay- and silt-size sediments. The most extensive area of lake deposits is in north- ern Ohio bordering Lake Erie. These deposits, and adjacent areas of wave-planed ground moraine, are the result of sedimentation and erosion by large lakes that occupied the Erie basin as Wisconsinan-age ice retreated into Canada. Other lake deposits accumulated in stream valleys whose outlets were temporarily dammed by ice or outwash. Many outwash-dammed lake deposits are present in southeastern Ohio far beyond the glacial boundary. Peat deposits are associated with many lake deposits and formed through the accu- mulation of partially decayed aquatic vegetation in oxygen-depleted, stagnant water.

A glacier occurs when the climate of an area is so cold that new snow does not completely melt each summer and more snow is added in the winter. After many winters the accumulation of this snow becomes compact and re-crystallizes, thus forming a glacier. Currently, glaciers cover about ten percent of the Earth's surface. Yet, in the past, glaciers covered much more land and were thousands of meters thick. (Tierney)

When the Ice Age began, the Rocky Mountain National Park area saw large ice sheets covering much of the land. There had been proof of earlier glaciation in the Rocky Mountain area because a mass of older rocks and sediments called moraines had been deposited by a glacier and found on the edges and extremities of the mountains there. Unfortunately, a large majority of the evidence has been erased by the more recent glaciation in the Ice Age.

The beginning of the Wisconsin Glaciation started about 75,000 years ago. The glacial maximum happened 14,000 years ago. The glacier was completely melted in Minnesota 11,000 years ago. There were four lobes in the Wisconsin glaciation. The Des Moines lobe extended into southern Minnesota, but missed the southeast and southwest corners of the state, which are known as Driftless areas. The extent of the Des Moines lobe to the south of Minnesota is marked by the Bemis moraine line.

I knew that both lateral and terminal moraines are formed when rocks and sediment are moved by glaciers, and that these moraines are left on the sides and front of glaciers, respectively. To me, this suggests that the rocks could only be deposited in lateral moraines, or in the terminal moraines if the glacier stops, changes directions drastically, or decreases in weight severely. If none of this occurs, the boulders will continue to be pushed. Therefore, the boulders mark the farthest outreach of one glacier, as long as no smaller glaciers occurred afterwards. One question that I have is: how long did it take for the largest glaciers to retreat to approximately the size of our glaciers today, if it ever did? Even though the movie repeatedly showed an digital animation showing the amount of snow and ice coverage in North America, the digital animation didn’t have any sort of a time scale. This animation showed that the glaciers covered most of North America, then retreated at some point, and increased in coverage again. I still am curious about how long it took for each of these transitions to

“Following Tertiary time during the Quaternary Period (the most recent 2 to 3 million years) the major sculpturing of Pacific Coastal Alaska began” (Anthony and Tunley 1976). Layers of snow deposited on the high mountains from moisture-laden winds of the Pacific. Over time, the snow compacted into ice; growing into large ice fields, moving, grinding, and carving out the landscape in a flowing movement to the sea. Glaciers advanced and retreated four times during the Quaternary Period (Anthony and Tunley 1976). Nunataks or isolated peaks projecting through ice or snow remained visible during maximum glaciation. “Maximum glaciation provided ice the ability to cap the Pacific Coastal Ranges and extend to the Gulf of Alaska or all the way to the

All of these erosion descriptions define glacial erosion created by alpine glaciers. Alpine glaciers are confined to mountain tops and valleys where it is cold and wet. A continental glacier can erode mountains and land masses just like alpine glaciers, but continental glaciers are not confined to mountains and valleys and they are spread over large distances. Glacial erosion will reshape mountains by forming cirques and reshape valleys by forming U-shaped valleys. Glaciers cut into the walls of its surroundings and cut into the bedrock as it slowly slides, which creates a u-shaped depression in the land. Glacial erosion reshaped many landscapes that are popular tourist sites today and assisted with the deposition of sediment to the lower lying regions and into rivers and

the west of the United States of America are also notable. The lakes of Canada

I. The first type of natural lakes are tectonic lakes which are formed from the movement of fault lines between mountains.

“Divided into two separate land areas, and bordered by four of the five Great Lakes, Michigan has the longest shoreline in the continental U.S. - nearly 3,300 miles.” [1] Michigan has a little bit of everything; mountains, hills and flatlands, forests, swamps, rivers, and many lakes, which hold 20% of the world’s fresh surface water. Michigan experiences all four seasons, especially winter in the Upper Peninsula. Water has shaped the state over thousands of years, making it what it is today, and none of this would have been possible without the water cycle.