Were the Great Lakes Ever Open to the Atlantic? – Part I

For some reason, Great Lakes theorists and even some others, find it difficult to accept the fact that the Great Lakes area was not the home of the Nephites, nor even would it have been possible for Lehi to have reached this area in 600 B.C.

During the last Ice Age, northern North America, including the northern United States and the Great Lakes region, was covered with glacial ice

    First of all, it is comparatively well known that during the last Ice Age, northern North America was covered by an enormous glacier, which alternately advanced and melted with variations in the climate. This continental ice sheet formed during the period now known as the Wisconsin Glacial Episode, or the Wisconsin Glaciation, and covered much of central North America between 30,000 and 10,000 years ago. As the ice sheet disintegrated, it created at its front an immense proglacial lake, formed from its meltwaters, as the retreat of glacial margins is not caused by a reversal of the glacier's flow, but rather from melting of the ice sheet (R. W. Ojakangas and C. L. Matsch, Minnesota's Geology, University of Minnesota Press, Minnesota, 1982, pp. 106–110). 
    It is important to keep this in mind, that is, that the Great Lakes were formed out of the melting glacial ice sheet. According to A.S. Dyke and V.K. Prest, among other geomorphological effects, this glaciation gouged out the five Great Lakes and the hosts of smaller lakes of the Canadian shield, filling with melt water, which extended from the eastern Northwest Territories, through most of northern Canada, and the upper Midwestern United States, including Minnesota, Wisconsin, and Michigan, to the Finger Lakes, through Lake Champlain and Lake George areas of New York, across the northern Appalachians into and through all of New England and Nova Scotia.
    At times, the ice sheet's southern margin included the present-day sites of northeastern coastal towns and cities such as Portsmouth, New Hampshire, Boston, New York City, and Great Lakes coastal cities and towns as far south as Chicago and St. Louis, Missouri—and then followed quite precisely the present course of the Missouri River up to the northern slopes of the Cypress Hills, beyond which it merged with the Cordilleran Ice Sheet ("Late Wisconsinan and Holocene History of the Laurentide Ice Sheet," Géographie physique et Quaternaire, vol.41, Num.2, 1987, pp237-263).
    As this glacier began melting northward about 10,000 years ago, to the west and north of the present Great Lakes area a huge lake, called Lake Agassiz, was formed, growing to cover some 170,000 square miles, including much of Manitoba, northwestern Ontario, northern Minnesota, eastern North Dakota and Saskatchewan, larger even than the Caspian Sea and approximately the size of the Black Sea. It was called Lake Agassiz, and fourteen shorelines have been identified of its original existence.

Lake Agassiz, the Traverse Gap, River Warren and the Glacial melt ran to the west of the Great Lakes area, not to the east of the region, discounting any huge bays or water areas open to the Atlantic Ocean

 

    Between Minnesota and South Dakota, within the Traverse Gap—an ancient river channel occupied by Lake Traverse, Big Stone Lake and the valley connecting them at Browns Valley, Minnesota—the River Warren was formed. When the Hudson Bay ice melted, the lake was completely drained—a  process involving five stages over a four thousand year period—into the Hudson depression, and the draining of the River Warren eventually led to the creation of the upper Mississippi River at Mendota, Minnesota, as well as the Minnesota River and the Red River of the North—a total of six rivers in all as well as Lake Souris, before it emptied, filling the Agassiz Basin.
    All these geological experts regarding the forming of the Great Lakes agree that these lakes were formed more or less in their present positions even further from the Atlantic Ocean than the distance is today. Yet, according to some, such as J. B. Mansfield (John Brainard Mansfield, History of the Great Lakes, Volume II, J. H. Beers &Co., Chicago, 1899), claim the Great Lakes were actually recessed Bays of the Atlantic coast. Mansfield writes extensively regarding evidences today of a large, currently buried riverbed that ran throughout the Great Lakes and around them, referred to as the Laurentian River system.
    It is important to note that before the Ice Age, this lost river that drained this region ran through the Toronto area. It had started from Lake Superior and flowed through the Lake Huron Basin, the Georgian Bay Basin and, through a valley in bedrock—now hidden by the Oak Ridges Moraine—to the Lake Ontario Basin and thence by the St. Lawrence Valley to the Ocean. However, this period of which he writes, indicating buried river beds that are said to have anciently existed throughout the Great Lakes area, predates the last ice age, which is considered to have ended around 10,000 to 12,000 years ago, or according to others, about 10,000 B.C., which makes Mansfield’s argument irrelevant regarding man’s use of the St. Lawrence river or its existence as a Bay of the Atlantic, for the post Glacial period is well known and understood. 
    To fully understand this, these river beds, beneath the rock surface seen today, are filled with glacial debris, otherwise known as moraine, that is regolith and rock, which is nothing more than an accumulation of earth, stones and sediment carried and finally deposited by a glacier, typically as ridges at its edges or extremity.
    As the ice sheet of the glacier melted, water began to pond in the divide between the moraine and the ice front, with the ice acting as a dam since the water was unable to drain through the ice sheet, which covered most of the proglacial river valleys. Numerous small, isolated water bodies formed between the moraine and the ice front, and as continued melting and receding northward, these ponds combined into proglacial lakes. Where there was no available outlet, water levels continued to rise until reaching one or more low spots along the rim of a moraine, or the ice sheet continued to retreat, opening access to a lower portion of the moraine.
    When the moraine debris was near the surface, having been depressed into the Earth from the weight of the glacier, but now released, it pushed upward after the glacial melting, and formed supraglacial sediments over the landscape, or hummocky, drum-shaped hillocks. composed of supraglacial sediments from the ice surface.
    According to Kurt H. Kjaer and Johannes Krüger, this active process forms or reworks moraine sediment directly by the movement of the ice, known as glaciotectonism, which pushes moraines and thrust-block moraines, which are often composed of till and reworked proglacial sediment ("The final phase of dead-ice moraine development: processes and sediment architecture, Kötlujökull, Iceland," Sedimentolog, vol.48, no.5 , 2001, pp 935–952).
(See the net post, “Were the Great Lakes Ever Open to the Atlantic? – Part II,” regarding whether or not the Great Lakes region was open to the Atlantic Ocean in ages past)