A few years ago, a book, What If?: Serious Scientific Answers to Absurd Hypothetical Questions, posed the question: what would happen if a tiny 10-meter (33-foot) hole opened up in the Mariana Trench?
First off, the author explains, some pretty cool things would happen.
"I want to get one thing out of the way first," Randall Munroe said on XKCD.
"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 and suck it through. Cooool."
In the hypothetical scenario, the 10-meter (33-foot) hole is, in fact, a portal, so any water that escapes through it wouldn't be able to re-enter the Earth's water cycle. The hole is at the bottom of the deepest part of the ocean, the Challenger Deep, and the water gets dumped on Mars (why not?).
Munroe explains that at first, not much would happen. The oceans are huge. Even though water would rush out of the portal at astonishing speed, the oceans would only drop by less than a centimeter (0.4 inches) a day.
"There wouldn't even be a cool whirlpool at the surface – the opening is too small and the ocean is too deep," Munroe said.
However, after a few hundred thousand years the Earth would change a lot. New underwater islands would be revealed, lands divided by seas would become connected once more, and the Earth would start to look very different indeed.
Can't picture it? Well, there's no need. An enthusiastic Redditor, Vinnytsia, has created an animation showing the world's oceans draining away through this hypothetical plughole.
It's very cool.
Vinnytsia explains on Reddit how they made the animation, using information from the Natural Earth Oceans and Lakes and Reservoir data sets. They also used an open source government Global Relief Model map and "the math for calculating the time is based on a simplified version of the Bernoulli incompressible flow equation".
In short, they were extremely thorough with their model. You can check out a full explanation of how they made it on the Data is Beautiful post, it's just as cool as the map itself.
If you'd like to know what would happen to Mars once all this water was dumped there through the portal, Randall Munroe explains that on his website too.