Transcript Inner Structure of the Earth 3. Mantle

Internal/External
Forces
of the
Earth
Inner Structure of the
Earth
1.Inner Core—dense and solid
2.Outer Core—Molten or liquid
• Both are mostly hot and
made of hot metal (iron)
Inner Structure of the
Earth
3. Mantle—thick layer of rock
(1800 miles thick); mostly
solid, but has pockets of
magma (melted rock)
4. Crust—very thin layer;
rocky surface
·
Below the oceans, the crust is
about 5 miles thick. Below the
continents it averages 22-75
miles in thickness.
Inner Structure of the Earth
Internal Forces that
Shape Landforms
1.Volcanoes—form when
magma inside the earth
breaks through the
crust. Lava flows and
may produce a large,
cone-shaped mountain
Internal Forces that
Shape Landforms
2.
Fault—a break in the
earth’s crust. Movement
along a fault can send out
shock waves, causing an
earthquake.
The Plate Tectonic Theory
1. The lithosphere—the
earth’s crust and upper
layer of the mantle—are
broken into a number of
large, moving plates.
The Plate Tectonic Theory
2. The plates slide very
slowly over a hot, pliable
layer of mantle.
3. The earth’s oceans and
continents ride atop of
the plates.
The Ring of Fire
A circle of volcanic
mountains that are
surrounding the
Pacific Plate
The Ring of Fire
2. Hot Spots: hot regions deep
within the mantle that
produce magma, which rises to
the surface. Volcanic island
chains form as oceanic plates
drift over the hot spot.
Example: Hawaiian Islands.
What Happens
When
Plates Meet?
Converging (Collision) Zone
They collide and push slowly
against each other and form a
collision or converging zone.
•If 2 oceanic plates collide, 1
slides under the other.
Islands often form this way.
Converging (Collision) Zone
•If 2 continental plates
collide, mountains are
formed. Example: Himalayas
Continental Crush (Collide)
They meet, or CONVERGE
and form a subduction zone.
*If an oceanic plate collides
with a continental plate, the
heavier oceanic plate will
slide under the lighter,
continental plate. Results:
volcanic mountain building and
earthquakes.
Subduction
SPREADING ZONE
Plates pull away from each
other and form a spreading
zone. These areas are
likely to have earthquakes,
volcanoes, and rift valleys
(a large split along the
crest of a mountain).
Spreading Zone
Fault
At a FAULT, the plates will
grind or slide past each
other rather than colliding.
Example: San Andres Fault.
External
Forces of
the
Earth
Weathering
• Changes in the earth’s surface
over thousands or millions of
years
• Breaks down rock at or near
the earth’s surface into
smaller pieces
Weathering
• Weathering is either
mechanical or chemical,
depending on the forces
involved.
Mechanical weathering
• rock is actually broken or
weakened physically.
Mechanical weathering
Frost Wedging: most common
form; water freezes to ice in
a crack (water expands 10%
when frozen). Ice widens the
crack and splits the rock.
Mechanical weathering
• Seeds: Seeds will take root
and grow in the cracks of a
rock. As the plant grows,
the rock will split.
Chemical Weathering
• Alters the rock’s chemical
make-up by changing the
minerals that form the rock.
Most important forces are
water (H2O) and carbon
dioxide (CO2).
Chemical Weathering
• Carbonic Acid: CO2 from the
air or soil combines with H2O
to make carbonic acid. When
the acidic water seeps into the
cracks in certain rocks
(limestone) it dissolves the
rocks away. Examples: caves
Chemical weathering
• Acid Rain: Chemicals in the
polluted water combine with
water vapor and then fall back
to the earth as acid rain. Acid
rain destroys wildlife, pollutes
water, destroys forests, and eats
the surface of buildings, statues,
and natural rock formations.
Chemical Weathering
• Acid Rain is known to be
caused by industrial
pollution, volcanic activity,
and acid producing agents
in the oceans.
Erosion
• The movement of weathered
materials such as gravel, sand, and
soil.
• An agent of mechanical weathering
• Three common forms
–Wind
–Water
–Glaciers
Erosion—Wind
• Most damaging in areas that
are dry and with few plants
• Wind-blown sand carves
and/or smooths natural and
man made formations
Erosion—Water
• Moving water carries
sediment
• Grinds away rock like
sandpaper
• Forms canyons and valleys
Erosion—Glaciers
• Huge, slow moving sheets of ice
• Carry dirt, rocks, boulders
• Movement carves out huge
basins
• When melted, leave behind piles
of rock/debris called moraines
• Great Lakes formed by glaciers