[First_Salute]

Valles Caldera

I wonder that the Valles Caldera of the Jemez Mountain Range, though now classified as "resurgent," was initiated by impact.

I suspect that an impact where the Earth's magma subsurface level is "just right," effectively "fractures" the crust of the earth and in slow motion, resembles something like this:

Combine High Speed and Time Lapse, BMumford.com

Ulysses Patera on Mars, showing two impact craters of later dates than the resurgent structure.

The smaller impacts did not cause "fractures." While the larger, older impact did, causing a large outward plume, some of which then collapsed back upon the hole, the heat and heat of vibration smoothing the matter --- whereas in the case of the Valles Caldera, the resulting splash is Redondo:

It's just a theory.

[blam]

A good possibility. I read a report about the 1628BC eruption of Thera and a guy (Mike Baillie) speculated that it may have been initiated by a comet fragment impacting. (not likely in my opinion)