#All
Hi, Kamron–
>> This could only occur if the sections were broken apart and then the crust
spread some and the sections fell over.
This is by no means the _only_ way to form thrust-fault-block mountains.
This can happen from stretching – it is called a graben. The crust thins as it
is stretched, growing depressed in the region affected. Blocks fall into the
depression and tilt. The falling would be in the region of fastest thinning,
which would not be the center of action. Expect a very broad valley with
shallow stepped walls, and a shallow crust/mantle boundary.
But let a magma flow push up the surface layers, and then let the pressure
fade; the blocks of crust may slide back into place tilted in a manner similar
to a graben. But I would not expect a depression to result in many such cases;
there may be no valley walls for the block bounds to concentrate at, and the
peaks may tend to be similar in altitude instead of stepping down as in a
graben. These would tend to be linear features if the original volcanic
activity was driven by a subduction at a nearby coast (I believe the Cascade
Mts. are such a volcanic arc, which may develop into the center of a region of
thrust-fault-block mountains with time).
Or let an igneous intrusion cool into a granite batholith underground; since it
is less dense than some rocks, it may rise after cooling. Depending on its
symmetry, it may tilt up one block – I have read that the Sierra Nevada Mts. of
Calif. may have formed that way.
There are doubtless other ways to get fault-block mountains.
–Doug