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Thread: Great Lakes Earth: The Americas

  1. #1 Great Lakes Earth: The Americas 
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    In a worldbuilding project I've been working on for years, some scientists have created satellites capable of something that seems science fiction for now — punching the walls of the universe to study an alternate reality. By that scenario, some hundreds of “alternate Earths” from hundreds of alternate universes would already have been discovered and meticulously studied. As much as half of them would still be ruled by humans, unfolded by events that turned out differently. One universe, for example, had an Earth where 9/11 never happened, or where the outcome of the Revolutionary and Civil Wars ended up differently.

    One of the most interesting to note was a planet that scientists call “Alternate Earth 111”, known to the public as “Great Lakes Earth”. Why? Because at first glance, it seemed that almost every continent is dominated by lakes, even those larger than the Great Lakes that we have in North America.


    Here is the whole map:




    Dark brown=mountains. Light brown=uplifts. Black=Igneous provinces still visible today at their original extent with no consideration of erosion.


    After some thought and experience, I thought it best if, rather than dump the whole info at once, we could participate better if we focus on one region at a time, starting with the Americas.

    The Appalachian Range used to exist, but all that remains nowadays are their metamorphic bedrocks. Since then, the Atlantic Coast is a labyrinth of islands, straits, channels and sounds, making New England the eastern equivalent of the Inside Passage, caused by five million years of being repeatedly scraped and bulldozed by ice. The terrain is not quite dramatic, the tallest above sea level being only 122.2 feet (37.25 meters.)

    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 20,310 feet. 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 55 million years ago as the result of a collision between eastern and western North America. They stopped becoming active as recently as nine million years ago. Since then, a series of faulting had shed off the mountains’ sedimentary skin and exposed the tougher granite-and-gneiss core. No wonder, then, that transdimensional explorer Mark Greene called the Great Lakes Earth Rockies “a single, continuous spine of breathtaking Tetons.” West of the Rockies stands an uplift varying in elevation above sea level between 2,000 and 13,000 feet (between 610 and 3962 meters.)

    Minor differences in geological history could create major differences in geographical shape. Without the Cascades or the Alaska Range, the distinctively whiplike Alaskan Peninsula simply does not exist. The area we’d recognize as San Andreas (Baja Peninsula and southwestern California) is fused into what we’d call southeastern Alaska. Evidence in the rocks beneath the soil shows that San Andreas did indeed collide with Alaska only 24 million years ago, but the mountain-building period did not last long, and the peaks were reduced into quarter-mile-tall hills.

    The Black Hills of South Dakota don’t exist on Great Lakes Earth. The Ozarks, larger in area and elevation than back home, are the closest analogy. The tallest stands 7242 feet (2207 meters) above sea level. They started life as a dome of granite that, over millions of years, had been replenished with fresh supplies of magma. This allowed the crystals that made the granite dramatically larger, making the rock itself a lot harder. After 2.2 billion years under the surface, the dome popped above sea level only as recently as 20 million years ago. Even though rain and river played a part in carving the dome into numerous spires, pillars and gorges, the real player in shaping the Ozarks is lower air pressure, exfoliating the surface into pieces like layers of onions.

    True to the spirit of the planet’s name, North America is full of large lakes. The largest of which is Agassiz. In fact, it is the cornerstone of all of Great Lakes Earth’s great lakes — enormous depressions, tectonic rifts or volcanic calderas reshaped and filled in by ice, rain and river. 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. This is Lake Agassiz, 95,000 square miles and 5500 feet at its deepest. Agassiz started out as a series of prehistoric rifts and faults that failed to split the continent. The valley wouldn’t become a lake until the ice bulldozed the depressions during the Pleistocene glaciations.

    West of the Rockies, there are even more lakes—Bonneville, Carson, Olympia, Hamilton and Red Deer. All of them formed separately late during the Cenozoic as tectonic weaknesses sank the land, sometimes to the point below sea level. Further shaping the lakes were the last five million years of ice ages strengthening and weakening the freeze-thaw cycles. As a result, not only do they have their distinctive shapes, they are also deep. Bonneville, the deepest, is currently over a thousand feet deep.

    What we’d presume to be the Brooks Range in northern Alaska actually isn’t. The Murchison Mountains, as we call them, are actually volcanic peaks standing 14,411 feet (4392 meters) above sea level at the tallest. They stand at one of the points where the Arctic Plate sinks beneath the Laurasian Plate.

    The Yellowstone mantle plume is still present. Except that instead of Wyoming’s northwestern corner, it can be found in northeastern California. The upland itself covers an area of 5,000 square miles and stands almost like an island between the surrounding lakes and lowlands.

    Five million years ago, the oceanic Panamanian Plate had been invaded on both fronts—by the Caribbean Plate in the northeast and the Pacific Plate in the southwest. This uplifted the basaltic slab to above sea level and had volcanoes guarding the plateau. The Twins, as they are called, are still active. One twin is currently 6,684 feet above sea level, the other 9,698 feet. Curiously, the Twins make up the coastline of Central America on Great Lakes Earth, which makes sense considering their young age. What doesn’t make sense is how they could be so tall in so short a time. The same problem is said of the Andes, which also make up South America’s entire western coastline. But if we look at a bathymetrical map, we start to understand why—from Argentina to Guatemala, the Pacific Plate is paralleled by the younger, narrower Nazca Plate. It first formed only ten million years ago and uplifted the Andean coastline for five million years before reaching the Panamanian Plate. This double-subduction may explain why the Andes, 25,122 feet above sea level and still rising, as they have been for the last 45 million years, had such devastating eruptions in the last 10,000 years, with an average of one eruption measuring eight on the VEI every thousand years.


    Questions follow:


    • Are these changes enough to spare northeastern Nebraska from the onslaught of Tornado Alley without sacrificing the Midwest’s prairie fertility in the process?
    • Will all these lakes and rivers (not pictured) turn the Wild West into a greener Eden?
    • How much of the Amazon Basin will still be rainforest?


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    Time Lord Paleoichneum's Avatar
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    I would anticipate less tornados, and a desert environment rather than a bread basket plains


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