April 28, 2004

San Diego: America's Former City

If a 3000-foot-wide asteroid hit downtown San Diego, all hell would break loose. Quite literally.

Here in La Jolla the 8.4-Richter-magnitude quake wouldn't start for four seconds after impact. Hardly enough time to pack up and load the SUV, let alone look up and go, "What was that?"

Problem is, before you even had time to think of saying "What was that?", the fireball, 288.9 times larger than the sun's diameter in the sky, would have already arrived. And it would stick around for 33 seconds, causing everything to, well, pretty much burn.

But then, we've all dealt with fire, how bad could it be? La Jollans would only have some 64 seconds to contemplate that notion, because that's how long after the blast before we'd be greeted with the arrival of rock, soil, buildings, bits of Petco Park, Sports Arena roof, Lindbergh Field runway, trees, water, aircraft carriers, transit buses, cars, everything else made of atoms.

A hurricane-scale wind? Hardly. Wind is simply too tame a word to use to describe the phenomenon. Asteroid impacts don't create wind. A more formal word, something a bespectacled post-doc in a white labcoat would readily say during a phone interview on Science Friday, something Latin... something like, say, "ejecta". Yes, the ejecta would be arriving in La Jolla at around 3,710 miles per hour, pretty much guaranteeing everything taller than a thumbtack would be flatted in a split second. Not a good time to be hang-gliding over Black's Beach.

And be sure to be wear earplugs: the noise of the air blast would be around 134 decibels.

But even if you manage to make it through the shake, the bake, and the ejecta, there's still the problem that if you were deep down in your La Jolla bunker, you, your house, your street, your neighborhood, and everything including Mount Soledad, would be gone, because the final crater would measure some 15 miles wide, and no doubt it'd fill with water from the Pacific after a pretty gnarly tsunami.

This bleak scenario in inspired by playing around with a very interesting website tool called "Earth Impact Effects Program" by Robert Marcus, H.J. Melosh, and G.S. Collins at the Lunar and Planetary Laboratory at the University of Arizona. The tool lets you fill in the blanks for a number of different parameters (size, distance from impact, etc) for a hypothetical asteroid hit, and then you can sit back and read the report and weep.

Luckily, the scenario outlined above is supposed to happen only once every 2.7 million years. So maybe we'll luck out and it'll be a while yet, and hey, maybe it'll hit somewhere else.

Posted by brian at April 28, 2004 10:10 PM

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