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2005-03-13 -Short Attention Span Theater-

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Posted by Mrs. Davis 2005-03-13 5:23:05 PM|| || Front Page|| [11130 views since 2007-05-07] Top

#1 I have disagreed with Dr. Melosh about this. Keep in mind that he is not a geologist.
One problem with this scenario is the apparent expectation of large amounts of melted rock. At these energy levels, dissipating into a massive solid, the difference between the melting point, about 1500 C, and the boiling point, about 2800 C, is not at all enormous.
Keep in mind as well that the energy density in any particular part of the affected area is inversely proportional to the square of the distance from the center.
This means that the zone in which we could expect the rock to melt, but not vaporize, is comparatively narrow. Much of the liquified material could be well within the zone of dislocation by blast, since this component of the energy yield would be enormously high as a percentage of the total.
If so, a large part of the molten material would be blown into the atmosphere by blast and dislocation effects, where it would condense and re-crystallize as ordinary rock and dust.

Posted by Atomic Conspiracy 2005-03-13 5:52:12 PM|| 2005-03-13 5:52:12 PM|| Front Page Top

#2 I thought thermal was inverse r-cubed, with shock waves inverse r-squared. That makes the melted region even narrower.

To my untrained eye, Barringer looks an awful lot like Sedan.

Posted by Dishman 2005-03-13 6:17:52 PM|| 2005-03-13 6:17:52 PM|| Front Page Top

#3 the difference between the melting point, about 1500 C, and the boiling point, about 2800 C, is not at all enormous.

Hmmm, AC. Are you forgetting the extra heat needed for the state change from liquid to vapor? Water, for example, needs about 500 times more heat to vaporize than to change its temp 1 degree C. Too lazy to look up silicon!

Posted by SteveS 2005-03-13 6:57:52 PM|| 2005-03-13 6:57:52 PM|| Front Page Top

#4 Man, youse guys take all the fun out of a perfectly good cataclysm.

Posted by Shipman 2005-03-13 8:15:09 PM|| 2005-03-13 8:15:09 PM|| Front Page Top

#5 Big Rock hit Arizona made big hole :)

Posted by djohn66 2005-03-13 9:24:27 PM|| 2005-03-13 9:24:27 PM|| Front Page Top

#6 Giant rocks from space: why do they hate us?

Posted by Seafarious 2005-03-13 9:28:13 PM|| 2005-03-13 9:28:13 PM|| Front Page Top

#7 Latent heat of vaporization

Posted by Bobby 2005-03-13 9:37:33 PM|| 2005-03-13 9:37:33 PM|| Front Page Top

#8 Anything emanating from a point source will form a sphere. The area of the sphere is 4 pi r^2. so the energy is inversely proportional to the square of the distance.

But actually, pie are round, cornbread are squared.

Posted by Alaska Paul 2005-03-13 9:49:02 PM|| 2005-03-13 9:49:02 PM|| Front Page Top

#9 What's the issue here? Meteors make big holes. I've seen one of the biggest existant - Wolfe Creek. Man thats a big hole.

Posted by phil_b 2005-03-13 10:36:57 PM|| 2005-03-13 10:36:57 PM|| Front Page Top

#10 "Hmmm, AC. Are you forgetting the extra heat needed for the state change from liquid to vapor? "Water, for example, needs about 500 times more heat to vaporize than to change its temp 1 degree C. Too lazy to look up silicon!"

I probably should know that but I don't. I do know that water has a very high specific energy of state change compared to other substances, which is one reason steam power is so effective. A rock will not actually vaporize under these conditions since it is essentially a gross mixture of different compounds in the form of crystalline minerals. What will happen is that some constituent compounds will vaporize while others remain liquid or even solid, producing a tremendous explosion.

"I thought thermal was inverse r-cubed, with shock waves inverse r-squared."

The first is true for a purely thermal phenomenon such as expanding steam. In the case of a meteor impact, most thermal effects are a conversion of shock effects and follow the same energy density profile.

Posted by Atomic Conspiracy 2005-03-13 10:40:24 PM|| 2005-03-13 10:40:24 PM|| Front Page Top

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