Download IE 2.1 Earth`s Crust in Motion

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Earth’s Crust
in Motion
Inside Earth Chapter 2.1
Pages 54-61
• Stress is the measure of the
amount of force applied to a
given area.
Effect on Rocks
• Stress is the force that acts on a rock to change
its shape or volume
• Adds energy to the rock.
• Deformation: Any change in the shape or
volume of Earth’s crust (caused by stress)
• Crust deforms from the force of plates
– Transform boundaries.
Relieving Stress
• Over time, stress builds up in the plates
• Eventually, the stress is released…
• The shaking and trembling that results from the
movement of rock beneath Earth’s surface.
• Releases MASSIVE amounts of energy
• Generates seismic waves
• Definition: Squeezing
• Effect on Rock:
• Makes rock layers thicker and shorter
• Associated Fault Type:
– Reverse Fault
• Associated Plate Boundary:
– Convergent Boundary
• Definition: Pulling apart
• Effect on Rock:
– Stretches making rocks longer and thinner
• Associated Fault Type:
– Normal Fault
• Associated Plate Boundary:
– Divergent Boundary
• Definition: Moving in opposite directions
– Think of shears or scissors
• Effect on Rock:
– Stress distorts the shapes of rocks.
• Associated Fault Type:
– Strike-Slip
• Associated Plate Boundary:
– Transform
• A fault is a break in the lithosphere
• Usually occur along plate boundaries, where
the motions of plates compress, pull or shear
the crust so much that the crust breaks.
• 3 Types of Faults
– Strike Slip Fault
– Normal Fault
– Reverse Fault
Hanging Wall
• Above the fault plane.
Hanging (head) Wall
Foot Wall
Foot Wall
• Below the fault plane
Hanging (head) Wall
Foot Wall
• Hanging Wall
– Lantern
• Foot Wall
– Path
Friction along Faults
• How rocks move determines how much
friction there is between opposite sides of the
• Friction: a force that opposes the motion of
one surface as it moves across another
What about the surfaces causes friction?
– It exist because surfaces are not perfectly smooth.
Normal Fault
• Force: Tension
• Hanging wall: Moves
down (with gravity)
Reverse Fault
• Force: Compression
• Hanging wall: Moves up
(against gravity)
Strike-Slip Fault
• Force: Shear (transform)
• Rocks on both sides of the
fault slide past each other
• Topography: determined by
its elevation, relief and
• All landforms have elevation
and relief
• A landform region is an area
where the topography is
• The height above sea-level
on Earth’s surface.
• The difference between
the highest point of
elevation and the lowest
parts of an area
– Mountains have high relief
– Plains low relief.
• Have high elevation and relief
– Perfectly smooth on top
• May be really thick (1,500m),
streams or rivers can cut through.
• Flat or gently rolling land
with low relief and
varying elevation.
• Depends on location…
– Coastal Plains have low
elevation at or near sea
level along the coast.
– Interior Plains are away
from the coast, causing
varied elevation.
• A landform with high elevation and relief
• Mountain Ranges are groups of mountains
that are closely related in shape, structure and
Mountains formed From Faulting
• Normal Faults uplift blocks
of rock and the hanging wall
Mountains formed From Folding
• When continental plates collide, stress can
cause rock layers to fold.
• Creates bends in the rock layers
– Himalayas Mts.
– Appalachian Mountains
• A term used to describe folds in rocks
• An arching fold in the rock layers or “apex”
• A downward pointing fold or “slump”
What to Work On
• Read Section 2.1 (pages 54-61)
• Answer section review questions
(page 61, #1-4)