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Who?

Unfortunately, I could not find any background information about Jeffrey Linn, but he is better known for his sea level maps. Specifically, what a particular city would look like if sea levels rose to a particular degree:

enter image description here enter image description here The Salish and Willamette seas with the Olympic Island (Images, apparently, were just too big.)

The same as above, only closer.

The whole of Cascadia

Palm Springs

enter image description here

enter image description here

enter image description here

The entire Seattle Archipelago in one link.

enter image description here

Now I chose the entire West Coast for a specific reason. The detail was done in the context of the melting of all the world's ice caps, which makes sense because less ice means higher sea levels and more ice means lower sea levels (ice age cream, anyone?)

In this alternate Earth, the entire West Coast is shaped just like the Linn projections, but they are not caused by the rhythmic retreating or advancing of polar ice caps. What else could create such a coastline?

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closed as unclear what you're asking by Shadowzee, Vincent, elemtilas, rek, Cyn Feb 22 at 5:43

Please clarify your specific problem or add additional details to highlight exactly what you need. As it's currently written, it’s hard to tell exactly what you're asking. See the How to Ask page for help clarifying this question. If this question can be reworded to fit the rules in the help center, please edit the question.

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    $\begingroup$ Its your alternative earth. You decide how your landmasses are created. The entire process might as well be random anyway. Any number of factors can effect the terrain. Tectonic plate movement/shape/number, erosion from the wind, rain and sea, the type of material the coast is formed from, comets, glaciers and volcanic activity. $\endgroup$ – Shadowzee Feb 21 at 22:32
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    $\begingroup$ I suggest removing all reference to that person and their art, and reword your question in a general sense. Something like, "What natural process could cause coastlines equivalent to sea level rise, without melting the ice caps?" Or if you don't want wilder, non sea-rising causes... "What natural process could cause a rise in sea level, without melting the ice caps?" $\endgroup$ – BoomChuck Feb 21 at 23:14
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    $\begingroup$ I intended to edit this question to be more precise – you don't need so many images, and don't need to go on about Linn – but it's unclear if you're asking about the sea levels or the structure of the coastal features themselves, or both. Are you asking "How can the sea level be as high as shown here, without melting polar ice caps?" or "Would the west coast of North America look like this without historic glaciation?" or a combination? $\endgroup$ – rek Feb 22 at 1:10
  • $\begingroup$ ice caps don't actually effect sea level that much thermal expansion of the ocean water itself is a bigger effect. $\endgroup$ – John Feb 22 at 3:13
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Reality already thought of the answer, and congratulations, the west coast of North America is an example of it: tectonic sea level change.

So, North America is moving west relative to Africa. About two thirds of the west coast are active subduction zones. These are along Mexico, Cascadia, and Alaska. As other plates subduct under N. America, the plate is deformed and pushed up, just like the Andes in South America.

So why doesn't North America have an Andes mountain chain?

For reasons that weren't covered in my geology class, the west coast of North America can only be pushed up so high before something flat out cataclysmic happens - all of the land that was pushed back springs forward in a massive earthquake. If you, as a casual observer, measured where the sea level was before and after the quake, you would think that it had risen relative to the topography of the coast.

On your alternative Earth, a quake of truly mythic proportions began near San Diego. As the stored energy was released, the land under San Diego relaxed and both shot forward and lower than its previous elevation. This displacement caused a massive tsunami that rushes over the city, seemingly drowning it permanently. Another tsunami races across the Pacific, causing havoc thousands of miles away.

But it isn't over. The energy released also travels along the San Andreas fault, causing tectonic sea level change all the way to Northern California. There, the San Andreas intersects the Cascadia Fault. Offshore, the North American plate begins to spring forward over the Juan de Fuca plate. While the cities and people of California had no warning, those living in Portland and Seattle have about a half hour to evacuate before the tsunami hits.

It was never enough time.

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  • $\begingroup$ north america does not have an "andes" becasue the pasific plate in not being subducted, mostly because north america is parked over the old spreading center so it is being gently underplated instead. the land is already slowly faulting back to level, its not going to happen all at once but it probably is hte most believable way. $\endgroup$ – John Feb 22 at 3:12
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    $\begingroup$ The Cascadia fault will do what you want, but the San Andreas is the wrong sort of fault (strike-slip rather than subduction). You'll need to find some other way to sink California. $\endgroup$ – Mark Feb 22 at 3:32
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    $\begingroup$ Perhaps North America doesn't have the Andes because it's got the Sierra Nevada & Cascades instead? Which are crustal blocks tilted downwards to the west, with very steep slopes & exposed faults like this: static.gigapan.com/gigapans0/97145/images/97145-900x250.jpg and a central valley with sediments up to 6 mi/10 km deep. $\endgroup$ – jamesqf Feb 22 at 4:52
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Landmass moves into the ocean, displacing water.

When I get into the tub, the water level rises. You can produce a similar effect by introducing additional mass into the tub of your oceans, displacing water and causing a rise in sea level.

Where would this mass come from? Undersea volcanism can add landmass from some pressurized subterranean reservoir of magma. Perhaps a transient acceleration of heating caused by radionuclide decay increases geothermal heat? Maybe the Hawaiian hotspot gets superhot and Hawaii becomes a continent the size of Australia? Perhaps some cataclysm causes the Andes to slide into the Pacific.

In any case: the water rises and you get the desired effect without ice melting.

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    $\begingroup$ the total volume of the earths ocean basins is more or less constant, eruptions are counterbalanced by subduction and subsidence, and no new continental crust is being added. raising sea level that much would require a new deccan traps eruption, which will drastically change global climate. $\endgroup$ – John Feb 22 at 3:27
  • $\begingroup$ You've got a scale error here. To get the desired 65 meter sea-level rise, you need to find 23 million cubic kilometers of land. Magma doesn't compress very well, so you can't get it from a pressurized reservoir. You're going to need to get it from somewhere else -- erode the world's mountains down to sea level or something of that nature. $\endgroup$ – Mark Feb 22 at 3:27
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you have two choices sea level can rise or the land mass can sink. it is far easier to raise the sea level just warm the water, but that is not compatible with icecaps. alternatively lower the land mass.

the western half of the north american plate is raised in height thanks to running over the old pacific spreading center. Upwelling magma has literally displaced it upward. It is already faulting back to to its original level, this is why north america is one of only two continents with earthquakes spread throughout it. Your continent could just be further along the process, its an alternative earth nothing says all the geologic events in the past need to match exactly.

there are other methods but they all drastically change the global climate.

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