Naked Science Forum
Life Sciences => Marine Science => Topic started by: katieHaylor on 28/09/2017 13:58:30
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Jonathan asks:
They say, in the deepest parts of the ocean, the water pressure can be so immense, that it is equivalent to several elephants standing on a penny.
Due to this intense pressure, is it possible for a shipwreck to be "suspended" (cannot sink any deeper)?
What do you think?
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Interestingly enough, there was a book I read in high school with this exact same question in it. Such a thing cannot happen. If the pressure at the bottom of the ocean was high enough (which it isn't), water would turn into a high-pressure form of ice which is more dense than liquid water. Such a layer of ice at the bottom of a hypothetical super-deep ocean would prevent a ship from sinking any deeper. At least, if the ship was made of steel such would be the case. If it was made of wood, I don't know. I'll look into that.
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Yes, the pressure at depth can be immmense, but it is not pressure that causes object to be buoyant but density of the water compared to the density of the object. Water is relatively incompressible so even at the deepest parts of the ocean the water density only increases by 5%. That might be enough if the wreck had some residual buoyancy due to trapped air, so that it was only just sinking, but unless that air is within a vessel that can resist extreme pressure the structure would collapse at depth. The same goes for waterlogged wood, the pressure would squeeze out any trapped air.
The only other thing that might have an effect is salinity. If you had a pool of very saline water at sea bottom this might give extra buoyancy- like Dead Sea - but salinity of ocean appears to be fairly consistent with depth. However, much of the ocean is unexplored so it might be possible - particularly near the poles where strong saline currents fall from under the ice.
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Due to this intense pressure, is it possible for a shipwreck to be "suspended" (cannot sink any deeper)?
If a submarine has "neutral density", it will float without rising or falling.
In certain places (such as the Straights of Gibralter), there is an Atlantic seawater inflow and a lower, denser, saltier outflow. By setting the neutral buoyancy midway, the submarine can sail through without using engines (there are suggestions that this has been used by submarines to avoid detection).
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the water pressure can be so immense, that it is equivalent to several elephants standing on a penny.
Air-filled objects like submarines get crushed if they go too deep.
The density of steel or titanium is much greater than water, so the wreck sinks.
For unmanned submarines, or external equipment pods on manned submarines, they fill all airspaces with oil.
Oil is non-compressible (so the pod can be made out of light material) and non-conductive (so electronics continues to work).
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The material making up the ship also compresses and increases in density. Even a solid steel sphere will see a slight reduction in its volume from the intense isostatic pressure.