Earth`s Crust in Motion

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Transcript Earth`s Crust in Motion

Earth’s Crust in Motion
Stress
• The surface of
the earth is
divided into 13
major tectonic
plates.
• These plates
interact with each
other constantly.
Stress
• The movement of
tectonic plates
create stress ( a
force that acts on
a rock changing
its shape and/or
volume.
3 Types of Stress
• The rocks reaction to stress is
called strain. The types of stress
are:
–Shearing
–Tension
–Compression
Types of Stress
Shearing: rocks break and slip past each
other horizontally as they are pushed in
opposite directions.
Tension: pulling of rock causes it to
become thinner in the middle (think of
stretching bubble gum after you chew it!)
Compression: rock is squeezed then
folds or breaks. (Pushing two things
together)
Faults/Fractures
• Breaks in rocks
create fractures.
• A fracture in
which there is
movement along
the line of the
break is called a
fault.
3 Types of faults
• Strike-Slip
• Normal
• Reverse
Normal Fault (Divergent boundary)
• Created by tension in which the hanging wall
moves downward relative to the footwall.
(Notice the way arrows are pointing)
Reverse Fault (Convergent boundary)
•Created by compression in which the
hanging wall slides up over the footwall.
(Notice the way arrows are pointing)
These
blocks
are
called
Fault
Blocks!
The
position of
a Fault
Block
determines
whether it is
a hanging
wall or a
footwall
Strik-slip Fault (Transform boundary)
•Created by shearing in which the
boundaries slide horizontally past each other.
Folding
A Fold is when rock layers bend due to stress in
the Earth’s crust.
Three types of folds:
•
•
•
•
Syncline
Anticline
Monocline
Types of Folds
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Syncline Fold
• Downward Arch
• Newer rock is pushed down toward the center of the fold
Anticline Fold
• Upward Arch
• Older rock is pushed up toward the center of the
fold.
Another Anticline Fold
Monocline Fold
• One side is vertically lifted higher than
the other side of the rock.
Folding Causes Mountains
• Folded (when rock layers are squeezed together and
pushed upward)
• Fault-block (faulting causes large blocks to crust to drop
down relative to other blocks.
• Volcanic (molten rock erupts onto Earth’s surface)