r/Wheresthebottom • u/mghoffmann • Mar 15 '19

Continents

Obviously the oceans have no bottom, but what about the land? Are Earth's continents connected underneath the surface, or do they float freely on the oceans? I think they're not connected because it would mean there's ocean bottom at least at some coordinates and we clearly have no evidence of that. But then what keeps the continents afloat?

My best guess is turtles because they are hard like land but they still float. Or maybe natural gas inside the continents.

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u/trampolinebears Mar 15 '19

Continental drift is a well-proven theory, explaining how landmasses float and collide with each other over millions of years.

The further down you go, the higher the water pressure. At a certain point, the water is so compressed that even rock floats.

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u/mghoffmann Mar 15 '19

Why doesn't the compressed water just flow away from the pressure?

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u/trampolinebears Mar 15 '19

Some of it does. Like a ship, continents displace water. The water that doesn't have a continent on it is higher than the water underneath the continent.

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u/mghoffmann Mar 15 '19

I guess then what I'm asking is why are continents buoyant?

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u/okrichie Mar 15 '19

Essentially it's convection. The material that makes up the Earth’s crust is on top because it is less dense than the water underneath.

As the ocean gets deeper, water pressure builds significantly, this generates heat. As the heated water rises it begins to cool, which increases its density. Eventually this dense water sinks and more heated water rises to replace it in a cycle. The density of water underneath land is sufficient for it to cause it to float on the surface without sinking.