Bye Bye Brontosaurus
Rocks from space. Most of us have stepped out into the backyard and looked up at the night sky to witness a wonderful, but brief, streak of light from a falling star. Hardly star size, those streaks originate from space bits as big as grains of sand. Larger things happen however. About once per year, a Volkswagen-size rock crosses Earth’s path. These zip from horizon to horizon, burning bright for 10 or 20 seconds --- long enough maybe, for someone with quick hand on a camcorder to catch the show for appearance on the evening news.
Thankfully the Earth’s atmosphere offers pretty good protection against space rocks. Any intruder less than about 50 meters in diameter likely vaporizes or disintegrates in passage to ground. Once a millennium perhaps, a rock large enough does make it through to strike Earth. If you’ve been to Meteor Crater Arizona you can understand the effects of say, a 100 m diameter space visitor landing at 20 or 40 thousand miles per hour. Fact is, the Earth is pock marked with many such craters (see figure).
What is the point of this tale? Sixty five million years ago an asteroid 10 km across struck near what is now Yucatan in Mexico. Between the blast wave, the molten ejecta tossed half way ‘round the globe, and the ‘zillions’ of tons of dust that fouled the atmosphere for years, I’m sorry to say that those poor dinosaurs didn’t make it.
In the end, I guess I’m not too worried about getting head-bonked by rocks from space. Far higher on my worry list are the consequences of a Volkswagen-size car blowing a tire next to me on the freeway, or of water damage from a clothes washer hose burst while I’m away. Still, next time I step out in the back yard looking for falling stars, maybe I wear a bicycle helmet just in case.
Steven N. Ward Santa Cruz
About OpenHazards Bloggers
Steven Ward is a Research Geophysicist at
the Institute of Geophysics and Planetary Physics, UC Santa Cruz. He specializes in the quantification and simulation of
natural hazards. Read Steve's blog.
John Rundle is a Distinguished Professor of Physics
and Geology at UC Davis and
the Executive Director of the APEC Collaboration for Earthquake Simulations. He
chaired the Board of Advisors for the Southern California Earthquake Center from 1994 to 1996. Read John's blog.
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