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 – 0533/animations/ch14_animations/animation2.htmlhttp:// 0533/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”.

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 VisualizationsExploring 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