Geography 2240A/B Lecture Notes - Carbonaceous Chondrite, Impact Crater, Chondrule
18 Mar 2013
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Chapter 14 impacts from space - the basics. I"ve chosen to begin this chapter with a schematic figure of impacts and growth of earth from those impacts. One million years ago an asteroid impacted at zhamanshin in kazakhstan, making a crater 13. 5 km in diameter (because impact was in a mountainous area that has since been severely eroded, photographs are of very poor quality). It (apparently) did not produced quite enough disruption to equal what we refer to as a "nuclear winter" (fig. 2), and it certainly was not big enough to cause global mass extinctions; however, we recognize that an impact like that, today, could easily end our civilization - which is very fragile - but certainly not our species. To emphasize our vulnerability, note that in 1989 astronomers were startled to see an asteroid roughly half the size of the one that caused the zhamanshin crater moving away from earth, having come within 700,000 km.
