US Disappears tomorrow, how does the world react?

[575]

Seems like the Adriatic area will provide more land for Italy and the Croatian/Dalmatian Archipelago will vanish. The minor change to the Med area must be because the underwater slope is more steep closer to the coast than say in the North Sea.
No risk of Venice drowning ITTL.
Some Greek islands will enlarge and Euboia become part of the mainland.
The Egypthians is going to have ancient Alexandria back above the waves.
Bangladesh may well be saved ITTL as the Maldives and a lot of other islands.

[belushitd]

stevep -

As far as the isostasy issue goes, you're looking at a mile thickness of ice that was removed rapidly in geologic terms, and remarkably fast in human terms. I think the low estimates are something like 100 years for substantial removal of the ice sheet. Ice is approximately 1 gram per cubic centimeter (roughly. I know its actually 0.917 gm/cm-3, but the math is MUCH easier if you go with 1 gram.) A mile is 1,609 meters, so a mile of ice exerts about 1,609,000 grams or 1,609 kilograms on each square centimeter of ground.

Rock is much denser. There's a lot of variety, but the normal number used for rock is 3.5 grams per cm-3. This is 3.5 times the density, so you're looking at, for a mile of rock, 4,800 (roughly) kg per square cm. There is, in fact, an isostasy calculation that can be performed to figure this out. Since I'm lazy, I'm going to link to a page here people.carleton.edu/~stitus/teaching/220/isostasy.pdf that has it already done. Its down the bottom of page 3, and the end result is that for every kilometer of erosion, you get 860 meters of isostatic rebound.

So.... Say we're going to do the calculation for a mile of crustal removal. That means we're looking at 0.86 * 1.609. We're going to get 1.3 kilometers of rebound. The question is, how fast? Here's a website geo.libretexts.org/Courses/University_of_California_Davis/UCD_GEL_56_-_Introduction_to_Geophysics/Geophysics_is_everywhere_in_geology.../03%3A_Planetary_Geophysics/3.4%3A_Isostasy that shows isostasy with a delta T unit in the calculations. Unfortunately, its been long enough since I took differential equations so that I am unwilling to attempt to figure it out with an instantaneous delta T, and figure out the resulting pressure equation to compare that pressure to the shear strength of rock at that depth to determine if its going to be a very rapid and energetic result or a long sigh from the planet as it looses some of its quarantine weight.

I am assuming it would be a fairly rapid rise in the beginning, possibly bringing the resultant bedrock above the water surface within a year or so, in the middle of the Rockies/Sierra Nevada ranges. Maybe the flatirons in Colorado, or the Front Range as well.

Anyway, the reduction in weight would likely provide a reduction in friction along the subduction zones on the west coast of the US and even more so on the gulf of Alaska. Faster movement under the north american plate would put additional stress on the oceanic plate at the edges of the removal, (Vancouver and Yakutat) which would likely result in additional earthquakes. All kinds of fun stuff.



EDIT - Almost forgot... If we're going to have 27 meters of sea level drop, that's pretty much going to cause a tsumani that will circle the world multiple times. I was going to use the tsunami from the 1964 Good Friday earthquake as an illustration, but I am unable to find a reference that describes the volume of water that was displaced.

Look at it this way... That earthquake affected roughly 600 miles of the fault in the Gulf of Alaska in a strip 200 or so miles wide. The greatest deflection was about 30 vertical feet. If we continue with those assumptions, you're looking at a wave 30 feet high starting at the coasts and rushing into the vacant space formerly occupied by rock.

The US coasts are roughly 12,000 miles. East Coast 2,100, Gulf Coast 1,200 miles Pacific coast, 1,900 miles. Total for the lower 48 is about 5,200 miles. Once the waves meet in the middle, they will rebound and immediately flow outwards. All coastal areas will be affected by, first, the massive drop in sea level cause by the draining into the American Sea, and then by the resulting tsunami as the waves rebound. 5,200 miles divided by 600 is about 8.6 times as much displaced water. The 1964 tsumani was measurable for 3 complete trips around the planet, which took, if I recall correctly, something like 2 or 3 days. I would hazard a rough guess that the tsunami from this event would go for closer to a month. 

End EDIT

Belushi TD

[stevep]

Jul 7, 2021 16:16:35 GMT belushitd said:

stevep -

As far as the isostasy issue goes, you're looking at a mile thickness of ice that was removed rapidly in geologic terms, and remarkably fast in human terms. I think the low estimates are something like 100 years for substantial removal of the ice sheet. Ice is approximately 1 gram per cubic centimeter (roughly. I know its actually 0.917 gm/cm-3, but the math is MUCH easier if you go with 1 gram.) A mile is 1,609 meters, so a mile of ice exerts about 1,609,000 grams or 1,609 kilograms on each square centimeter of ground.

Rock is much denser. There's a lot of variety, but the normal number used for rock is 3.5 grams per cm-3. This is 3.5 times the density, so you're looking at, for a mile of rock, 4,800 (roughly) kg per square cm. There is, in fact, an isostasy calculation that can be performed to figure this out. Since I'm lazy, I'm going to link to a page here people.carleton.edu/~stitus/teaching/220/isostasy.pdf that has it already done. Its down the bottom of page 3, and the end result is that for every kilometer of erosion, you get 860 meters of isostatic rebound.

So.... Say we're going to do the calculation for a mile of crustal removal. That means we're looking at 0.86 * 1.609. We're going to get 1.3 kilometers of rebound. The question is, how fast? Here's a website geo.libretexts.org/Courses/University_of_California_Davis/UCD_GEL_56_-_Introduction_to_Geophysics/Geophysics_is_everywhere_in_geology.../03%3A_Planetary_Geophysics/3.4%3A_Isostasy that shows isostasy with a delta T unit in the calculations. Unfortunately, its been long enough since I took differential equations so that I am unwilling to attempt to figure it out with an instantaneous delta T, and figure out the resulting pressure equation to compare that pressure to the shear strength of rock at that depth to determine if its going to be a very rapid and energetic result or a long sigh from the planet as it looses some of its quarantine weight.

I am assuming it would be a fairly rapid rise in the beginning, possibly bringing the resultant bedrock above the water surface within a year or so, in the middle of the Rockies/Sierra Nevada ranges. Maybe the flatirons in Colorado, or the Front Range as well.

Anyway, the reduction in weight would likely provide a reduction in friction along the subduction zones on the west coast of the US and even more so on the gulf of Alaska. Faster movement under the north american plate would put additional stress on the oceanic plate at the edges of the removal, (Vancouver and Yakutat) which would likely result in additional earthquakes. All kinds of fun stuff.

Belushi TD

  belushitd,

  Bloody hell that's fast!  It's even longer since I've even looked at differential equations That means if only a shallow submersion then for areas with a lot of height above sea level now, such as the Rockies that's going to rebound pretty damned quickly.  That would minimise the longer term impacts as you would probably have a continuous land bridge, probably quite wide in some places between Canada and Mexico within a decade if not less.  So just as the Earth is getting used to a sea link between the Atlantic and Pacific its closed again.

  Thanks

  Steve

[SpaceOrbisHistory]

Feb 1, 2021 16:18:36 GMT american2006 said:

So the scenario, tonight at midnight EST America just disappears into the ocean, all 50 states, DC, and territories and all embassies and military bases are restored to there natural form. All other American properties stays. How does the world react?

So the land area of the US just falls under the waves. Well one easy fallout of this is that over 300 million people are dead. So a mass death thing right out the gate so that's no good. Another is the world just one of the most technologically advanced military powers in a day. So I would guess alot of places are going to see moves made. US based companies now cease to exist or fail due to this happening. So I would guess people are going to find their money is gone and we enter into a new great depression.