Horizontal Compression:
* Shortening: Yes, horizontal compression *generally* leads to shortening of the crust. Imagine squeezing a piece of clay – it gets shorter along the direction of squeezing. This happens because the rocks are being pushed together, causing them to fold or fault.
* Thickening: This is where it gets more complex. While compression does lead to the buildup of material, it doesn't always mean thickening in the way you might think.
Why Thickening isn't always straightforward:
* Folding: Compression often causes rocks to fold. While folds can make the crust thicker in certain areas, they can also cause thinning in others, depending on the folding pattern.
* Faulting: When compression is strong enough, it can cause rocks to break and form faults. This can lead to blocks of crust being uplifted (thickening) in some areas and pushed down (thinning) in others.
* Crustal Flow: In some cases, under extreme pressure, the crust can behave like a very viscous fluid. This can lead to horizontal flow and even sideways thickening, but it's a complex process.
In Summary:
* Horizontal compression *generally* leads to shortening and some thickening.
* The degree of thickening depends on factors like the type of deformation (folding vs. faulting), the rock types involved, and the intensity of the compression.
* It's crucial to remember that compression can lead to both thickening and thinning in different parts of the crust.
Let me know if you'd like to explore any specific examples of horizontal compression and its effects!
