Great Lakes Earth: The Americas
Related to http://earthscience.stackexchange.com/questions/7077/if-the-oceans-were-deeper
The Appalachian Range, at first glance, doesn’t seem so different—low-lying hills covered in forest dominating the eastern landscape. However, they are taller—7,244 feet above sea level at the highest, compared to Mount Mitchell back home, which is over 6500 feet above sea level. An even more radical difference is its history. Back home, the Appalachians first appeared 480 million years ago as the result of a collision between North America and Africa. On Great Lakes Earth, the Appalachians are no older than two and a half billion years, the result of several volcanic uplifts. Indeed, the Appalachians on Great Lakes Earth are a labyrinth of solid gneiss and granite, a macrocosm of the Black Hills, which we have but Great Lakes Earth doesn’t.
The mountains of the American West have some major differences. For starters, only the Rockies stand firm—no Coast Range and most certainly no Sierra Nevada. Like the Appalachians, the Rockies on Great Lakes Earth have a different road from ours. If we connect the following dots from our North America, we might have an idea as to how the Rockies in Great Lakes Earth might be arranged:
• Kugluktuk, Nunavut, Canada
• Yellowknife, Northwest Territories, Canada
• Calgary, Alberta, Canada
• Williston, North Dakota, United States
• Rapid City, South Dakota, United States
• Lamar, Colorado, United States
• Clovis, New Mexico, United States
• Ciudad Juarez, Mexico
• San Luis Potosi, Mexico
• Tampico, Mexico
While our Rockies vary in width from 70 to 300 miles, their Rockies vary between 75 and 200 miles. While our Rockies stand no taller than 14,440 feet above sea level, the tallest peak in a Great Lakes Rockies is measured to be 14,505 feet. Not only that, they aged differently as well. Back home, our Rockies formed between 80 and 55 million years ago through the Laramide Orogeny, the subduction of the North American and Pacific Plates at a shallow angle. Their Rockies first formed 120 million years ago as the result of a collision between the the St. Lawrence Limestone and the continental Laramia. 371
They stopped becoming active shortly before the dinosaur extinction. Even so, the rate of decay in Great Lakes Earth is significantly smaller than back home, for the main rocks are schist, granite and gneiss, tough rocks with small vulnerabilities.
True to the planet’s name, North America is full of large lakes. The largest of which is Agassiz. To have an idea on the shape, size and scope of Agassiz, we must look at the familiar faces of the Great Lakes—Superior, Michigan, Huron, Erie and Ontario—and then flood off the entire basin. That is Lake Agassiz, 95,000 square miles and 257 meters deep on average. Agassiz started out as a few tectonic depressions that expired some 20 million years ago. They wouldn’t become one lake until the ice bulldozed the depressions during the Pleistocene glaciations.
There are great lakes west of the Rockies as well. What we’d recognize as western Utah is for them Lake Bonneville, 25,000 square miles and a thousand feet deep. Lake Bidahochi in northeastern Arizona is over 30,000 square miles in area and is the source of the Colorado River. Unlike Agassiz, the tectonic depressions in Bonneville and Bidahochi are still volcanically active. Only six times in Great Lakes Earth’s recent geologic history did ice carve these lakes into the distinctive shapes that we can see today.
Comparing Great Lakes Earth to ours, we’d find that all land below sea level has become water, and Death Valley, the continent’s lowest and hottest point, is no exception. In its place is Lake Manly, a long but narrow strip of water fed by rivers flowing from Bidahochi.
It’s interesting that if we see the West Coast of Great Lakes North America, we’d see a real different shape. While the Atlantic coastline is similar to ours, the Pacific coastline looks as though 75 meters of sea level have risen.
It is up north, from British Columbia to Alaska, that the iconic peaks of the Cascades stand firm. What we’d recognize as the Alaska Range in southern Alaska is an extension of the Cascades, turning the over 20,000-foot Denali into America’s largest volcano.
The Yellowstone mantle plume is still present. Except that instead of Wyoming’s northwestern corner, it can be found in northeastern California. 188