Chapter 11 Deformation of the Crust
II. HOW MOUNTAINS FORM
- a mountain is the most extreme type of deformation
- Mount Everest is the Earth’s highest mountain and continues
to grow taller every year
A. Mountain Ranges and Systems
1. mountain range – a series of mountains that are closely
related in orientation, age and mode of formation
2. mountain system – a group of mountain ranges that are
adjacent
3. mountain belts – the largest systems are part of two larger
systems a. circum-Pacific belt – forms a ring around the Pacific
Ocean b. Eurasian-Melanesian belt – runs from the Pacific
Islands through Asia and Southern Europe and into
Northwest Africa.
B. Plate Tectonics and Mountains
- scientists believe that most mountains from as a result of
collisions between tectonic plates
1. Collisions Between Continental Crust and Oceanic Crust a. oceanic lithosphere subducts beneath continental
lithosphere b. produces such a large-scale deformation of rock that
high mountains are uplifted c. causes partial melting of subducted oceanic lithosphere d. may eventually form volcanic mountains on Earth’s
surface e. accretion – the process in which a terrane becomes part
of a continent
2. Collision Between Oceanic Crust and Oceanic Crust a. volcanic mountains commonly form b. eruption of magma form an arc of volcanic mountains
on the ocean floor c. Mariana Islands
3. Collisions Between Continents a. no subduction due to equally dense lithospheres b. uplifted the Himalayas

c. Himalayas continue to grow because the plates are still
colliding
C. Types of Mountains
- scientists classify mountains according to the way in which
crust was deformed and shaped by mountain-building
stresses
1. Folded Mountains and Plateaus a. folded mountains – a mountain that forms when rock
layers are squeezed together and uplifted b. plateaus
1b. large, flat areas of rock high above sea level
2b. form when thick, horizontal layers of rock are slowly uplifted so that the layers remain flat instead of faulting or folding
3b. can also form when layers of molted rock harden and pile up on Earth’s surface or when large areas of rock are eroded
2. Fault-Block Mountains and Grabens a. fault-block mountains
1a. a mountain that forms where faults break Earth’s crust into large blocks and some blocks drop down relative to other blocks
2a. Sierra Nevada range of Nevada b. grabens
1b. long, narrow valleys that form from the same faulting that forms fault-block mountains
2b. develop when steep faults break the crust into blocks and one block slips downward relative to surrounding blocks
3. Dome Mountains a. dome mountain – a circular or elliptical, almost
symmetrical elevation or structure in which the
stratified rock slopes downward gently from the central
point of folding b. forms when magma rises through the crust and pushes
up the rock layers above the magma c. may also form when tectonic activity gently uplifts rock
layers

d. Black Hills of South Dakota and Adirondack
Mountains of New York
4. Volcanic Mountains a. volcanic mountains – forms when magma erupts onto
Earth’s surface b. commonly form along convergent plate boundaries c. mid-ocean ridges are some of the largest that form
along divergent boundaries d. hot spots
1d. volcanically active areas that lie far from plate boundaries
2d. Hawaiian Islands