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Originally Posted by mugaliens
By contrast, had the same mass hit the planet, intact, we'd probably have had another event similar to the K/T extinction event.
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Originally Posted by cjl
Not likely. The K/T event was caused by an asteroid on the order of 6 miles across. Tunguska was a few tens of meters across.
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Ok, let's call it 70 m. Compare that to the roughly 300 m chunk which formed the mile-wide Meteor Crater in Arizona, and the 2000 m chunk behind K/T.
Assuming roughly equivalent velocities, and since KE is proportional to mass, which is proportional to the cube of the diameter, letting a 70 m chunk equal a factor of 1, we have the following:
70 m: 1 (if Tunguska had not broken up, but had struck the Earth)
300 m: 79 (meteor crater)
2000 m: 23,324 (K/T)
However, the factor for the 70 m assumes it struck Earth. Tunguska did NOT. Rather, it broke up high altitude, and in the process accelerated a large air mass to mach velocities. It's this accelerated air mass which struck the Earth, and toppled the trees for miles around. Nothing of the original mass remained at that point except chunks ranging from dust through bb's, to bullets, and a few sizes as large as shotgun slugs. The rest was probably aggregated but small chunks of ice which broke up before turning to water, and perhaps steam.
Comparing the actual Tunguska event to the above scale, since it didn't impact with the Earth itself, the Energy it imparted to the ground was considerably less than it would have been with a direct impact, at least by one order of magnitude, giving Tunguska a high .1 on that scale.