Transcript MOUNTAIN BUILDING

MOUNTAIN BUILDING
MOUNTAIN FORMATION
1. orogeny = processes that form all mountain ranges
a. creates broad, linear regions of deformation known as
orogenic belts
b. most belts are associated with plate boundaries
2. mountains = natural landforms that reach high elevations
a. usually have narrow summits and steep slopes
b. rise at least 600 meters above the surrounding land
Saladian Orogeny
3. mountain range = group of adjacent mountains with same
general shape and structure
Ex: Mount St. Helens is part of Cascade Range
4. mountain system = group of adjacent mountain ranges
Ex: The Great Smoky, Blue Ridge, Cumberland, and
Green mountain ranges = Appalachian mountain
system in eastern United States
Antarctic Mountain range
5. mountain belt = large group of mountains including mountain
ranges and mountain systems
a. two major belts
1) Circum-Pacific belt = rings Pacific Ocean
2) Eurasian-Melanesian belt = runs across northern Africa,
southern Europe, and Asia
b. both meet in Indonesia, just north of Australia
c. both belts are located along convergent plate boundaries
6. form when plates collide
a. continental and ocean plate
b. two ocean plates
c. two continental plates
7. continental margin = boundary between continental crust &
oceanic crust
a. two types:
1) active = occur along plate boundaries
2) passive = do not occur at plate boundaries
b. mountain building takes place near active margins
Changes in Earth’s Crust:
1. due to weight (addition or removal) of some part of crust
a. when thicker and heavier will sink more into mantle
b. when thinner and lighter will rise higher on mantle
2. up and down movements occur because of two opposing
forces
a. crust presses down on mantle
b. mantle presses up on crust
c. forces are balanced crust does not move up or down
3. isostasy = balancing of two forces
a. isostatic adjustments = up and down movements of crust
to reach isostasy
b. during adjustments areas of crust are bent up and down
c. pressure created causes rocks in that area to deform
d. occurrences areas
1) constantly in areas with mountain ranges
2) where rivers flow into large
bodies of water carrying
large amounts of sediment
3) where glaciers once covered
the land
4. principle of isostasy = parts of crust will rise or subside until
these parts are buoyantly supported by their roots
a. mountain ranges have thick roots of continental material
that extend into mantle
b. as mountains erode and mass becomes smaller, roots will
become smaller
c. balance between erosion and decrease in size of root will
continue for hundreds of millions of years until both
mountains and their roots disappear
5. isostatic rebound = slow process of crust’s rising as result of
removal of overlying material
deformation = bending, tilting, and breaking of earth’s crust
Types of Mountains
1. folded mountains = rock layers buckle and fold due to being
squeezed from opposite sides
a. highest mountain ranges in the world
b. show evidence of faulting and igneous activity
Ex: Appalachian Mountains (oldest in North America)
Himalayas, Alps, Ural Mountains
Himalayas
2. fault-block mountains = crust is broken into large blocks and
lifted above surrounding crust
a. faulting tilted blocks form gently sloping mountains
b. one block is pushed up while the other block is pushed
down
Ex: Grand Teton Mountains, WY
c. grabens = long, narrow valleys formed when large blocks
of crust have dropped between normal faults
Ex: Death Valley, CA
Yosemite
d. horsts = forms when block of crust is thrust upward
between two normal faults
Ex: Basin and Range Province of Nevada
e. ocean ridge mountain ranges can be thousands of km wide
f. pillow basalts = igneous rock formed when magma pushes
through dikes and erupts onto seafloor
Located in Nevada
3. volcanic mountains = when molten rock erupts onto surface
a. develop on land or ocean floor
b. largest found on divergent plate boundaries of mid-ocean
ridge
c. peaks can rise above sea level to form volcanic islands
d. hot spots = pockets of magma beneath crust that erupt
onto surface
Ex: Mt. St. Helens, WA [land]
Mauna Loa, Hawaii [hot spot]
Iceland [volcanic island]
Mt. Baker
4. dome mountains = molten rock rises through crust and
pushes up rock layers above it
a. forms a circular dome on earth’s surface
b. also referred to as uplifted mountains
c. isolated structures that tend to occur in areas of
essentially flat-lying sedimentary rocks
d. eventually rock wears away in places leaving separate
high peaks
Ex: Black Hills, SD
Adirondack Mountains, NY
Yellowstone