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MOUNTAIN BUILDING –student notes
1. ______________ – refers of all changes in the original shape or size of a rock body.
______________ deformation – at the earth’s surface, low temperatures and low
pressures, solid rock fractures
______________ deformation – deep with in the Earth, high temperatures and high
pressures, rock is deformed without breaking
The mineral composition and texture also affects how it will deform.
Small stresses applied over time will cause the rock to bend.
2. Stress and Strain
______________ – force per unit area acting on a solid
______________ – the change in shape or volume
______________ stress – causes a material to be stretched
______________ stress – causes a material to shorten
______________ stress – causes a material to be distorted
3. Folds – during mountain building flat-lying sedimentary and igneous rock are bent
into a series of ripples
______________ – arching of rock layers
______________ – downfolds or troughs
______________– large step-like folds
4. Faults – fractures in the crust along which movement has taken place
______________– when the hanging wall block moves down relative to the footwall
block, caused by tensional forces
______________– the hanging wall block moves up relative to the footwall, caused by
compressional forces
______________– reverse faults with dips less than 45o
______________faults – the movement is horizontal and parallel, caused by shear stress,
San Andreas fault
______________ – most common rock structure, fractures along which no appreciable
movement has occurred
5. Mountains – classified by the dominant processes that deformed them
______________ Mountains – formed by folding, ______________ stress is the major
force that formed them; examples – Appalachians, Alps, northern Rocky Mountains
______________Mountains – mountains that form as large blocks of crust are uplifted
and tilted along normal faults; examples – Tetons Range, Sierra Nevadas
Horst and Grabens – formed from tensional forces, horsts are uplifted structures and
grabens is where the blocks dropped down; example – the Basin and Range region of
Nevada, California and Utah
______________ – formed by upwarping and exposing older igneous and metamorphic
rock; example – Back Hills of South Dakota
Basins – downwarping structures having a circular shape
6. Mountain Building – ______________
Mountain Building at Convergent Boundaries – colliding plates provide the
compressional forces that deform rock
Oceanic-Oceanic Convergence – forms ______________arcs, Aleutian Islands of Alaska
Ocean- Continental Convergence – ocean crust subducts the continental crust, the
continental crust is deformed, creates volcanic arcs on continent
Accretionary wedge – accumulation of different sedimentary and metamorphic rocks
Continent-Continent Convergence – form ______________ mountains; examples –
Himalayas, Ural mountains
Mountain Building at Divergent Boundaries – fault-block mountains
Non-Boundary Mountains – Hawaiian Islands are volcanic islands formed by a
______________
Continental Accretion – smaller crustal fragments collide and merge with continental
margins; example – many of mountains rimming the Pacific Canada and Alaska
______________ – any crustal fragment that has a geologic history distinct from
adjoining terranes
______________ – a floating crust in gravitational balance. As mountains erode, the
crust rises in response to the reduced load. Erosion and uplift continue until the
mountains reach normal crustal thickness
The weight of the ice sheet during the Pleistocene depressed the Earth’s crust hundreds of
meters. Since the ice age, uplift has occurred
DRAWINGS: