Transcript Mountain Building

Mountain Building
An uplifting experience!
How and where?
• Deformation of crust from stress.
– Compression = Rocks are squeezed together
• Occurs at convergent boundaries
– Tension = Crust is stretched apart
• Occurs at divergent boundaries
• Build-up of crust from volcanic activity.
– Accretion (build-up of magma) inside crust stretches
crust (tension) or erupts and accumulates on surface.
– Occurs above subduction zones and “hot spots”
FOLDING
• Rocks bend without breaking
• A response to compressional stress
• Upward folds are called anticlines
– These form mountain ranges
• Downward folds are called synclines
– These form valleys between ranges
– http://www.wiley.com/college/strahler/0471480
533/animations/ch14_animations/animation2.
html
Faulting
• Vertical Faults
– Normal and Reverse
– Defined by movement of “hanging wall”
relative to the “foot wall”.
• Horizontal
– Strike-slip
– Results from “shear stress”
– Occur along transform boundaries
Normal Faults
• Form as a result of tensional stress
– At divergent boundaries or above subduction
zones.
• Hanging wall slides down the foot wall.
• The exposed footwall forms a cliff called a
“fault scarp”.
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http://www.pbs.org/wnet/savageearth/animations/index.html
http://www.classzone.com/books/earth_science/terc/content/visualizations/es1103/es1103page01.cfm?chapter_no=visualization
Reverse Faults
• Form as a result of compressional stress
– At or near convergent plate boundaries
• Hanging wall moves up relative to the foot
wall.
• If hanging wall gets pushed up and over
the foot wall it is known as a “thrust fault”.
• Often occurs along with folding.
Fold Mountains
• Form in collision zones from compression.
• Form large systems with many ranges.
• Examples:
– Appalachian Mountains (past)
– Alps (still forming)
– Himalayas (still forming)
– Rocky Mountains (past)
Fault-Block Mountains
• Usually form above subduction zones or
continental hot spots.
– Rising magma= tensional stress = normal
faults.
• Examples:
– Teton Range (Wyoming)
– Sierra-Nevada mountains (CA)
– Exploring Earth Visualizations
Tetons
Volcanic Mountains
• Form above active subduction zones or hot
spots where magma erupts from the crust.
• The erupted materials pile-up aroune the vent,
forming a mountain.
• Examples:
– Some of the Cascade range (Oregon and
Washington)
– Some of the Andes mountains
– Mountains of Japan, Phillipines, Indonesia