Re: Plate techtonics and asteroid hits

On Jun 24, 7:42 pm, "Noelie S. Alito" <noe...@xxxxxxxxxxxx> wrote:
Lorentzwrote:
On Jun 24, 3:55 pm, Timberwoof <timberwoof.s...@xxxxxxxxxxxxxxxxxxxxx>
wrote:
In article <1182666507.006759.157...@xxxxxxxxxxxxxxxxxxxxxxxxxxxx>,

Lorentz<drosen0...@xxxxxxxxx> wrote:
On Jun 24, 12:40 am, Timberwoof
<timberwoof.s...@xxxxxxxxxxxxxxxxxxxxx> wrote:
In article <1182649144.687412.233...@xxxxxxxxxxxxxxxxxxxxxxxxxxxx>
Lorentz<drosen0...@xxxxxxxxx> wrote:
On Jun 23, 1:19 pm, UC <uraniumcommit...@xxxxxxxxx> wrote:
On Jun 23, 1:13 pm, "chris.linthomp...@xxxxxxxxx"
<chris.linthomp...@xxxxxxxxx> wrote:
On Jun 22, 4:49 pm, UC <uraniumcommit...@xxxxxxxxx> wrote:
On Jun 22, 4:41 pm,Lorentz<drosen0...@xxxxxxxxx> wrote:


Hence, I wanted to disconnect the idea of "collision" with "brittle
object." Even in models where collision takes place, the earth can't
be treated like a brittle object.

Aye, but a bolide represents a lot of energy within a
small amount of time, so we would expect a "brittle"
response, rheologically speaking.

I have a real good counterexample. Look at the moon through a
telescope. It is covered with craters, most of which were really
formed by meteorites. There are no cracks emanating from these
craters, at least none that are easily seen from earth. The same goes
from large meteorite craters on earth, though ironically these are not
as easily available for inspection.

A rocky crust over large scales can not fracture. At geological
scales, it acts like a soft plastic. Fractures can't propagate in a
soft plastic. However, shapes could be preserved to some extent. That
is why one sees craters on the moon. But fractures? Seldom.

I am sure it happens sometimes that a bolide creates "fractures."
It must happen occassionally at least for small bolides. Maybe under
some conditions it happens with large bolides.

.