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January 21, 2005

Science: It’s Almost Full-Moon Time Again

-Martin Kite-Powell

 

 

 

Does anyone care to wager more notable seismic activity similar to what we witnessed last month and the month before? For example of course we had last month's unforgettable tsunami-causing 9.0 earthquake off the coast of Sumatra as well as the hardly unrespectable 8.0 quake between New Zealand and Antarctica along with other activity (including that strange anomaly in Venice where the duel effects of a full moon and low tides left the city dry for the first time since the 1930’s). November saw its share too on North America with volcanic rumblings at Mount St. Helens along with various shakers across the globe.

 

So the question is whether this month will see anything as dramatic. As a living thing, I hope not, but from the perspective of science my Schadenfreude admittedly gets the best of me. The sheer information about the Sumatra shaker’s eerily noticeable affect on the globe was enough to keep me up late many a night as I ingested it like a chocolate mousse at a tony London restaurant. Tasty tidbits included our losing a few miliseconds from our day on 26 December as the whole earth shook and subtly wobbled from the Sumatra quake - which can sound a bit scary from the perspective of our survival.

 

But then I found out that even an asteroid made of solid iron ore with a diameter of 20km (12.42 miles) traveling at 20km per second striking solid land at a 45° angle isn’t even enough to do the planet in or even “strongly affect” it. (Granted, you have a 200 mile crater, a 10.6 earthquake at point of impact along with a fireball, “fallout” 2500 feet deep, a max wind velocity in the impact zone of around 11,100 mph and a crash louder even than downtown traffic, but we’d still have most of our mass, remain on our axis and some of us would live another day.

 

In fact, to find an asteroid big enough to destroy the planet, you would need to find one of this sort but super-sized: at least 7,100 km (4409.10 miles) in diameter. (Granted, it doesn’t take that much to wipe out all life but still, this is some serious planetary constitution here). Such an asteroid has never struck since the formation of the earth – and the 20km variety isn’t scheduled for a few thousand generations either.

 

All this of course fascinates me but it also should be reassuring to most who are able to realize that it takes a whole lot to kick this ball off the playing field- and even the more serious nudge is few and far between even among purely terrestrial disasters. According to the United States Geological Survey (USGS), there are about 500,000 earthquakes detected each year, one fifth of which are noticeable without special instruments and of those, only 100 are strong enough to cause any damage. So it will be interesting to see what the January lunar cycle shall bring our modest planet in terms of a geologist's "to-do" list.

 

 

 

 

 

 

 

 

 

Some cool quick resources:

 

University of Arizona Department of Planetary Sciences Lunar and Planetary Laboratory Earth Impact Effects Program (interactive)

 

Space.com: How an Asteroid Impact Causes Extinction

 

Software: Keyhole “Planetary Interface” (and ultimate street map app)

 

Latest Earthquake Data from USGS: California Limelight

 

Is There an Earthquake in Your Future? Contact the Seismic Network

 

Details and Facts of the Sumatra Quake

 

 

Posted by Martin at January 21, 2005 02:53 AM

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