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Earth Science
Layers of the Earth
The
Earth’s
Layers
Lithosphere
• The top part of the
layer is the Earth’s
crust.
• The outermost layer
of the earth known as
the “rock sphere”
that we live on.
• It is divided into
pieces called
tectonic plates
Asthenosphere
• The soft layer of the mantle below the
lithoshphere.
• Tectonic plates move above this layer.
Outer Core
• The liquid layer below
the earth’s mantle.
• This layer surrounds
the inner core.
Inner Core
• The solid, dense center of our planet.
• It is about 6,374 km. beneath the earth’s
surface.
“Plate tectonics” Theory:
 explains motion/behavior of Earth’s lithosphere
Moves a few centimeters a year
 explains volcanoes, mountain building and
earthquakes
stiff lithosphere floats on top of weak asthenosphere
Plate tectonics  about a dozen or so plates
Supporting evidence
Modern
measurements
EARTH is a Heat Engine
What drives the plate movement?
Tectonic Plates
• The place where two tectonic plates meet
is called a plate boundary.
Plate Boundaries
3 types
 divergent boundaries
 convergent boundaries
 transform fault boundaries
• http://www.wwnorton.com/college/geo/eart
h2/content/chapter_4/animations.asp
PLATE
TECTONICS
2) Plate boundaries
 Divergent boundaries
Mostly mid-ocean ridges (seafloor spreading)
Typical spreading rates ~ 5 cm/year
As oceanic moves away from ridge, it cools, &
becomes denser
Also found where continents break apart
Example: Red Sea and East African Rift
Mid Ocean Ridges
http://earthquake.usgs.gov/learning/animations/
Continents Break Apart –
Rift Valley
PLATE
TECTONICS
2) Plate boundaries
 Divergent boundaries
Also found where continents break apart
Example: Red Sea
http://www.wwnorton.com/college/geo/an
imations/sea_floor_spreading.htm
PLATE
TECTONICS
2) Plate boundaries
Red Sea (looking southeast)
PLATE
TECTONICS
2) Plate boundaries
 Divergent boundaries
Continents breaking apart
Example: East African Rift
Red triangles show
the active volcanoes
and the Afar Triangle
(shaded, center)
Divergent Plate Boundaries
PLATE
TECTONICS
2) Plate boundaries
Convergent Plate boundaries
 Convergent boundaries
Subduction zones
ocean-continent
- Volcanoes
Examples: Mount St. Helens
ocean-ocean
- Volcanic island arcs
Examples: Marianas, Aleutians, Hawaii
continent-continent
- Mountain Building
Examples: Himalayas, Alps, Appalachians
continental crust and continental crust
• Mountain building
Oceanic and oceanic crust
• DEEPEST Trenches and Island Arcs
Oceanic crust
Oceanic crust
Continental Crust and Oceanic Crust
• Trenches and explosive volcanoes
volcano
Oceanic crust
Continental crust
Molten rock
SUBDUCTION
ZONE
• Mountains
• Volcanoes,
trenches &
earthquakes
PLATE
TECTONICS
2) Plate boundaries
 Transform fault boundaries
Strike-slip faulting
Plates slide past each other: no production/destruction
of material
STRESS
• Stress occurs at plate boundaries. Stress
causes rock to change shape or deform
(deformation)
Types of Stress: Type of boundary
– Compression
convergent
– Tension
divergent
– Shearing
transform
Stress Causes Deformation
Deformation
Bends and Breaks Rock
If you bump your bike into a large rock two
things can happen.
The metal can either bend or snap.
Stress Cause - Compression
Effect: Folding
• Folding- When rock layers bend because
of stress on the earth’s crust.
The types of folding are:
Folding
• Anticline- Arch shape
folds in the earths’
crust.
pushing
• Syncline- Trough
shaped fold in a rock.
pushing
Monocline
• Monocline – simplest
- involves a slight
bend on one side
Anticline
Anticline
Anticline
Folding
• Syncline- Trough
shaped fold in a rock.
Syncline
Syncline
Syncline
Syncline
Syncline
Monocline
• Monocline – simplest
- involves a slight
bend on one side
Monocline
Monocline
Monocline
Monocline
Monocline
Tectonic Plates
• The place where two tectonic plates meet is
called a plate boundary. (When there is
enough pressure that builds up on the rocks’
edges and earthquakes can occur).
• Earthquake Facts
Earthquake Animation
Tectonic Forces
• Faulting- Stress that causes rocks to
break
• Faults slide past each other.
• The types of faulting are:
- normal fault
- reverse fault
- strike-slip fault
Fault Type #1: Normal Fault
Cause: Tension/ Divergent movement
Normal FaultsEffect: The hanging wall moves down, relative
to the footwall. Normal because of the
pull of gravity.
Normal Fault
NormalFault
Normal Fault
Fault Type #2: Reverse Fault
Cause: Compression/ Convergent Movement
Reverse FaultEffect: The hanging wall moves up relative to the
footwall.
Reverse Fault
Reverse Fault
Reverse Fault
Reverse Fault
Strike-Slip Fault
Cause: shearing/ crosswise movement
Strike-slip FaultsEffect: When opposing forces cause rock to
break and move horizontally.
Strike Slip Fault
Strike Slip Fault
Strike Slip Fault
San Andreas Fault
• US Geological
Survey scientist
Chris
Mountain
Building
Newhall attaches a tape measure to a cliff
Cause:
Compression
on Bubuin Island. Activity from nearby
VolcanoUplift
Island
Bubuin
by 15
Effect:
– has
crustlifted
is raised
to higher
centimeters
elevation
Grand Canyon
Folded Mountains
• In a folded mountain range, the rock layers are
folded up.
Folded Mountains
• Fault-Block
• Folded
• Volcanic
Folded Mountains
Sierra Nevada
Folded Mountains
Appalachian
Folded Mountains
Appalachian Mountains
Fault-BlockMountains
• Fault-Block
Fault- Block Mountians
• Rock layers are tilted up and can have
sharp jagged peaks.
Fault-Block Mountains
Grand Tetons from Jackson Lake Lodge (WY) are
examples of fault block mountains.
Fault Block Mountain
Fault-Block Mountains
• Big Bend Texas
Volcanic Mountains
• Volcanic mountains are often cone shaped, and
form along convergent boundaries.
• Also forms along the divergent sea floor
spreading
Volcanic Mountains
Volcanic Mountains
• Mt. Ranier, Washington
Volcanic Mountains
Mt. St. Helens, Washington
Volcanic Mountains
Mt. Shasta, California
Volcanic Mountains
• Volcanic mountains of Guatemala make up
part of the Pacific's "Ring of Fire".
Popocatepetl, Mexico. December 12, 2007 this
volcano spewed lava and ash two miles high.
Volcanic Mountains
• Mt. St. Helens- Live
• On May 18, 1980, Mount St. Helens violently
erupted. For 2 months the volcano showed signs
that it was waking up from its 123-year sleep.
• Earthquakes beneath the mountain increased.
Steam and ash erupted.
• And a "bulge" grew on the mountain's steep north
side. All these warning signs signaled that magma
was moving upward inside the volcano.
US Volcanoes
• Cascade Range Volcanoes
• Major West Coast Volcanoes
• Hawaii Volcano Map