Download Earth`s Crust in Motion

Earth’s Crust
in Motion
CH 5 Prentice Hall
p.144-151
Stress(ed)?
• Feeling stressed? No not the
same stress,
• Stress is the measure of the
amount of force applied to a
given area.
•
Deformation
• Any change in the shape or volume of Earth’s
crust.
• The slow motion of Earth’s plates cause
deformation.
Effect on Rocks
• The force that acts on a rock to change its
shape or volume.
• Stress is a force- it adds energy to the rock.
• Energy is stored in the rock.
Earthquakes
• The shaking and trembling that results from
the movement of rock beneath the Earth’s
surface.
Compression
• Definition: squeezing
• Effect on Rock:
• Makes rock layers thicker and shorter
• Associated Fault Type:
– Reverse Fault
• Associated Plate Boundary:
– Convergent Boundary
Tension
• Definition: Pulling apart
• Effect on Rock:
– Stretches making rocks longer and thinner
• Associated Fault Type:
– Normal Fault
• Associated Plate Boundary:
– Divergent Boundary
Shear
• 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
Faults
• 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
•
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Hanging Wall
• Above the fault plane.
Hanging (head) Wall
Foot Wall
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Foot Wall
• Below the fault plane
Hanging (head) Wall
Foot Wall
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Friction along Faults
• How rocks move determines how much
friction there is between opposite sides of
the fault.
• Friction- a force that opposes the motion of
one surface as it moves across another.
– It exist because surfaces are not perfectly
smooth.
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Normal Fault
• Hanging wall moves
down.
• Due to tensional forces.
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Reverse Fault
• Hanging wall moves up.
• Due to compressional
forces.
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Strike-Slip Fault
• Rocks on both sides of the
fault, slide past each
other
• Shear- Forces
• San Andres Fault
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Landforms
• Topography- of an area is
determined by is elevation ,
relief and its landform.
• All landforms have
elevation and relief.
• A landform region is an
area where the topography
is similar
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Elevation
• The height above sealevel on Earth’s surface.
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Relief
• The difference between
the highest point of
elevation and the lowest
parts of an area.
• The slope of the land.
– Mountains have high relief
– Flat, rolling land- low relief
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Plateaus
• Has high elevation and a flat
surface.
• Perfectly smooth on top.
• May be really thick (1,500m),
streams or rivers can cut through.
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Plains
• Made up of flat or gently
rolling land with low
relief.
– Coastal Plain- lie along the
coast. – low elevation and
relief.
– Interior Plain- away from
the coast, elevation can
vary but relief is low.
• Great Plains- the central US.
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Mountains
• A landform with high elevation
and relief.
• Mountain Ranges- mountains
usually occur in groups of
mountains that are closely
related in shape, structure and
age.
• Himalaya Mts
• Appalachian Mts
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Mountain Building
• Over millions of years, fault
movement can change a flat
plain into a towering mountain
range.
• Mountains are formed by:
– Faulting
– Folding
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Mountains formed From Faulting
• Normal Faults uplift blocks
of rock and the hanging
wall drops.
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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
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Anticline
• A term used to describe folds in rocks
– An upfold in the rock layers
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Syncline
• Another term used to describe folds in
rocks
– A down fold
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Anticline/Syncline
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Anticline/Syncline
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