mountain building

converging continental plates

Two converging continental plates smash upwards to create gigantic mountain ranges (Figure 1.1). Stresses from this uplift cause folds, reverse faults, and thrust faults, which allow the crust to rise upwards. As was stated previously there is currently no mountain range of this type in the western U.S., but we can find one where India is pushing into Eurasia. (a) The worlds highest mountain range, the Himalayas, is growing from the colli- sion between the Indian and the Eurasian plates. (b) The crumpling of the Indian and Eurasian plates of continental crust creates the Himalayas.

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converging plates

Converging plates create the worlds largest mountain ranges. Each combination of plate types continent- continent, continent-ocean, and ocean-ocean creates mountains.

diverging plates

Amazingly, even divergence can create mountain ranges. When tensional stresses pull crust apart, it breaks into blocks that slide up and drop down along normal faults. The result is alternating mountains and valleys, known as a basin-and-range (Figure 1.3). In basin-and-range, some blocks are uplifted to form ranges, known as horsts, and some are down-dropped to form basins, known as grabens. (a) Horsts and grabens. (b) Mountains in Nevada are of classic basin-and-range form. Click image to the left or use the URL below. URL: Click image to the left or use the URL below. URL:

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subducting oceanic plates

Subduction of oceanic lithosphere at convergent plate boundaries also builds mountain ranges. This happens on continental crust, as in the Andes Mountains (Figure 1.2), or on oceanic crust, as with the Aleutian Islands, which we visited earlier. The Cascades Mountains of the western U.S. are also created this way. The Andes Mountains are a chain of con- tinental arc volcanoes that build up as the Nazca Plate subducts beneath the South American Plate.

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instructional diagrams

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questions

this mountain range is a continental volcanic arc.

-->  a) the cascades

b) appalachians

c) himalayas

d) the alps

this type of boundary creates the worlds largest mountain range.

a) divergent

b) transform

-->  c) convergent

d) none of the above

mountain ranges do not form at these plate boundaries.

a) divergent

-->  b) transform

c) convergent

d) none of the above. mountain ranges form at all types of plate boundaries.

the indian plate and eurasian plate converge to make this mountain range.

a) the cascades

b) appalachians

-->  c) himalayas

d) the alps

mountain ranges do not form at these convergent plate boundaries.

a) oceanic crust-oceanic crust

b) oceanic crust-continental crust

c) continental crust-continental crust

-->  d) none of the above. mountain ranges form at all types of convergent plate boundaries.

if you looked deep beneath the himalaya mountains you would find

-->  a) ancient oceanic crust

b) ancient continental crust

c) a lava ocean

d) all of the above

the andes mountains are made by

a) subduction of an oceanic plate beneath an oceanic plate.

b) tensional faulting.

c) compression of two continental plates.

-->  d) subduction of an oceanic plate beneath a continental plate.

in basin-and-range, blocks that are uplifted form ranges, also known grabens.

a) true

-->  b) false

horsts are

a) down-dropped rock that form basins

-->  b) uplifted rock that form ranges.

c) one the right side of a strike-slip fault.

d) on the left side of a strike-slip fault.

the mountain ranges lining the pacific ocean basin are due to

a) tensional forces.

b) shear forces.

-->  c) compressional forces.

d) none of these.

diagram questions

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