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The chosen location for this vault was quite strategic; from Wikipedia:
Spitsbergen was considered ideal due to its lack of tectonic activity and its permafrost, which will aid preservation. The location 130 metres (430 ft) above sea level will ensure that the site remains dry even if the icecaps melt. Locally mined coal provides power for refrigeration units that further cool the seeds to the internationally-recommended standard – 18 °C (0 °F). Even if the equipment fails, at least several weeks will elapse before the temperature rises to the -3 °C (27 °F) of the surrounding sandstone bedrock.Let's say that even though this thing is in a low-tectonic-activity area, a freak earthquake still happens. No problem: I read in a NYTimes article that the entrance to the vault "is designed to withstand bomb blasts and earthquakes." Also: "No one person has all the codes for entrance." Kinda like The Good, the Bad and the Ugly, except Scandinavian. And no gold. Okay, nevermind.
Most of the reasons I have heard for this thing existing always threw images from the end of Cat's Cradle into my mind... that is, if something were to wipe out everything on Earth, we would have enough seed samples to "start over" all thanks to the Global Seed Vault. Apparently though, its current biggest reason for being is to help prevent the extinction of seed genes, since gene banks all over the world seem to run into issues with management, funding, natural disasters, and equipment failures. "Now these scattershot efforts are being urgently consolidated and systematized, in part because of better technology to preserve plant genes and in part because of the rising alarm about climate change and its impact on world food production."
The Global Seed Vault has its own site, which includes a comprehensive list of all of the seed samples it holds. Right now there are half a million seed samples in there, and each sample has about 500 seeds in it... which brings it to about 250 million seeds. Wowzers.
There are a ton more interesting things about the Global Seed Vault; too much to write here. Like how it operates on a safety deposit box system re: the countries that submit seeds to it; or how recently Ireland sent over seeds for 32+ varieties of potatoes. Read more on the Wikipedia page!