Running Water

Deformation of the Crust
PANGAEA


Pangaea was assembled 290 m.y.
Continental collision produced the interior mountains -- 
Appalachian - Caledonian, Hercynian, and Urals
Features preserved in these uplifted areas allow the geologist 
to "see" the ancient oceans that were destroyed in the process

Continental Crust


Structure of continents exhibits a pattern:
	eroded remnants of very old deformed rocks in the interior - 
Shields
	more recent deformation in mountain systems closer to the 
margins
	oceans open and close and mountains are uplited and reduced 
by erosion

The Stable Interior


Cratons - extensive, flat, tectonically stable interior of the 
continents
Shields - parts of the craton consisting of crystalline basement 
rocks - composition, structure, and textures indicate periods of 
intense metamorphism, partial melting and the intrustion of 
magmas into the older rocks


OROGENIC BELTS

Most geologists believe that mountains form by plate collisions
Subduction when one plate is more dense that the other
Continent collision when two pieces of continental lithosphere 
collide
The Himalayan Orogeny


Subduction of India under the Eurasian Plate - 60 my
The main central thrust forms when India collided with Tibet 
- 40my
A second thrust formed about 20 my - the main boundary 
thrust
The Himalayas are "carved" from these two great stacks


The Appalachians


Valley and Ridge - Deformation in the Ordovician, Devonian 
and Permian
Blue Ridge - pC crystalline rocks - thrust over the Valley and 
Ridge
Piedmont - pC and Paleozoic metamorphosed rocks thrust 
over the Blue Ridge
Coastal Plain - relatively young rocks


The Cordillera


Complex of different types of orogenic zones
Volcanic Action - Cascades
Upwarped - Reverse Faults - The Front Range
Fault Block Mountains - Basin and Range
Folded Mountains - Appalachian
Stacking of thrust faults - Himalayas and Appalachian





Coastal Plain and Shelf


The Atlantic Coastal Plain began to form during the Triassic 
when the rifting that preceded the opening the Atlantic
Immature sedimentary rocks accumulated in the graben and 
were intruded by basaltic dikes and sills


Regional Vertical Movement



Epeirogeny - gradual upward and downward movements 
without significant deformation
Michigan Basin and the Black Hills are two prime examples
Cooling and contraction can produce basins and heating and 
expansion can produce domes