Transcript Mountain Building

Mountain Building
Unit 3: Lesson 3
Objectives:
Mountain Distribution
Convergent Boundary Mtns
Other Mountain Types
Crust–Mantle Relationships
When you look at a map of the
Earth, you immediately notice the
oceans and continents.
 Changes in elevation are best seen
by using a topographic map.
 Differences in elevation are not
caused by a difference in density.
 The Himalayans
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Isostasy
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The displacement of the Earth’s mantle by
the continental and oceanic crust is a
condition of equilibrium known as
isostasy.
The crust and the mantle are in
equilibrium when the force of gravity of
the crust is balanced with the upward
buoyancy of the mantle.
Similar to people getting into and out of a
boat. As people get in, the boat goes
down; as people get out, the boat rises.
Continental Buoyancy
Continents are said to float on the
mantle, because the continents are
less dense than the underlying
mantle.
 Mountain Building Video
 Let us discuss the different forces of
gravity and buoyancy in the next
slide.
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Isostasy Example
Isostasy and Erosion
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Since erosion works against mountains,
tearing them down, why do some
mountains still exists today?
As the mountain erodes, the mountain
root will disappear. This allows the crust
to rise, due to the buoyancy force, equals
the mountain’s force.
This slow process of the earth’s crust
rising as a result of the removal of the
overlying material, mountain, is called
isostatic rebound.
Convergent-Boundary
Mountains
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When one oceanic plate converges with
another oceanic plate, one plate descends
into the mantle and creates a subduction
zone.
As the material in the subduction zone
melts, some material is forced up to the
surface as magma and results in a
volcano.
The volcano grows until a volcanic
mountain is formed.
What would the soil or rock be like on this
mountain?
Oceanic-Continental
Convergence
This type of boundary also creates a
subduction zone.
 Can produce major mountain ranges
due to the uplift of the continental
plate
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Andes, South America
 Ring of Fire, Pacific Ocean
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Continental-Continental
Convergence
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The Earth’s tallest mountains are formed
by the convergence of two continental
plates.
The Himalayans are the world’s tallest
mountains, above sea level.
Instead of melting like at a subduction
zone, the material is folded and the
magma hardens underground adding to
the uplift.
Other Mountain Types
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Divergent Boundary Mountains
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Generally found along and comprising
the Mid-Atlantic Ridge. As sea-floor
spreading occurs, magma rises to fill
the gap and is built up over eons.
Uplifted Mountains
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Formed by the slow uplift of
continental material. The magma
has hardened below the surface and
is then forced up by the upward
force of the mantle.
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Adirondacks, New York
Volcanic Peaks
As the volcano mountain moves
away from the hot spot, the volcano
becomes dormant and eventually
extinct.
 Shield volcanoes make up much of
the Hawaiian Islands, are formed in
this manner.
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Greatest Mountains on Earth
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Video Compilation