From WhatIf (Randall Munroe)
How quickly would the ocean's drain if a circular
portal 10 meters in radius leading into space was created at the bottom
of Challenger Deep, the deepest spot in the ocean?
How would the Earth
change as the water is being drained?
–Ted M.
I want to get one thing out of the way first:
According to my rough calculations, if an aircraft carrier sank and
got stuck against the drain, the pressure would easily be enough to fold
it up[1] and suck it through. Cooool.
Just how far away is this portal?
If we put it near the Earth, the
ocean would just fall back down into the atmosphere.
As it fell, it
would heat up and turn to steam, which would condense and fall right
back into the ocean as rain.
The energy input into the atmosphere alone
would also wreak all kinds of havoc with our climate, to say nothing of
the huge clouds of high-altitude steam.
So let's put the ocean-dumping portal far away—say, on Mars.
(In
fact, I vote we put it directly above the Curiosity rover; that way, it
will finally have incontrovertible evidence of liquid water on Mars's
surface.)
What happens to the Earth?
Not much.
It would actually take hundreds of thousands of years for the ocean to drain.
Even though the opening is wider than a basketball court, and the water is forced through at incredible speeds,[2] the oceans are huge.
When you started, the water level would drop by less than a centimeter per day.
There wouldn't even be a cool whirlpool at the surface—the opening is too small and the ocean is too deep.[3]
(It's the same reason you don't get a whirlpool in the bathtub until the water is more than halfway drained.)
But let's suppose we speed up the draining by opening more drains.
(Remember to clean the whale filter every few days), so the water level
starts to drop more quickly.
Let's take a look at how the map would change.
Here's how it looks at the start:
And here's the map after the oceans drop 50 meters:
It's pretty similar, but there are a few small changes. Sri Lanka,
New Guinea, Great Britain, Java, and Borneo are now connected to their
neighbors.
And after 2000 years of trying to hold back the sea, the Netherlands
are finally high and dry.
No longer living with the constant threat of a
cataclysmic flood, they're free to turn their energies toward outward
expansion.
They immediately spread out and claim the newly-exposed land.
When the sea level reaches (minus) 100 meters, a huge new island off
the coast of Nova Scotia is exposed—the former site of the Grand Banks.
You may start to notice something odd: Not all the seas are
shrinking.
The Black Sea, for example, shrinks only a little, then
stops.
This is because these bodies are no longer connected to the ocean.
As
the water level falls, some basins cut off from the drain in the
Pacific.
Depending on the details of the sea floor, the flow of water
out of the basin might carve a deeper channel, allowing it to continue
to flow out.
But most of them will eventually become landlocked and stop
draining.
At 200 meters, the map is starting to look weird.
New islands are
appearing.
Indonesia is a big blob.
The Netherlands now control much of
Europe.
Japan is now an isthmus connecting the Korean peninsula with Russia.
New Zealand gains new islands. The Netherlands expand north.
New Zealand grows dramatically.
The Arctic Ocean is cut off and its
the water level stops falling.
The Netherlands cross the new land bridge
into North America.
The sea has dropped by two kilometers.
New islands are popping up
left and right.
The Caribbean Sea and the Gulf of Mexico are losing
their connections with the Atlantic.
I don't even know what New Zealand is doing.
At three kilometers, many of the peaks of the mid-ocean ridge—the
world's longest mountain range—break the surface.
Vast swaths of rugged
new land emerge.
By this point, most of the major oceans have become disconnected and
stopped draining.
The exact locations and sizes of the various inland
seas are hard to predict; this is only a rough estimate.
This is what the map looks like when the drain finally empties.
There's a surprising amount of water left, although much of it consists
of very shallow seas, with a few trenches where the water is as deep as
four or five kilometers.
Vacuuming up half the oceans would massively alter the climate and
ecosystems in ways that are hard to predict.
At the very least, it would
almost certainly involve a collapse of the biosphere and mass
extinctions at every level.
But it's possible—if unlikely—that humans could manage to survive.
If we did, we'd have this to look forward to:
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