Question
• Discuss the following with the people next to you:
• At what type of plate boundary do mountains form, and what is required
for very large mountians?
Shenandoah & Great Smoky Mountain National Parks
• Appalachian Mountains - How did they Form?
• Not close to a present-day boundary
• Clues = granites and metamorphic rocks
• Once as spectacular as the Himalayas - GC connection?
How Do Very Large Mountains Form
• What is a mountain?
– Thicker crust
• How does the crust get thicker?
– Compression - convergence
How Do Very Large Mountains Form
• Continental Collision the Himalayas......
• Making Thicker Crust
The Himalayas
1) 120 my ago -> plate with India breaks away from Antarctica
=> moves north at ~20 cm/yr
The Himalayas
2) Leading oceanic part of the plate subducted along southern Tibet -> partial
melting => Andean Arc
The Himalayas
3) 50 my ago -> oceanic crust entirely subducted => continental collision
-> igneous activity stops...
=> thrust faulting and folding => crustal shortening and thickening.…
=> suture zone -> plates welded together
Thrust Faults - thicker crust by stacking
The Himalayas
* Results in mountain chain of highly deformed sedimentary rocks plus associated
igneous and metamorphic rocks...
=> compression still active = continued uplift