Download fault-block mountains.

Deforming the Earth’s Crust
Faults and Folds
Chapter 7 Section 4
Deformation
• The process by which the shape of a rock
changes because of stress.
• There are two types of stress that occur in
rocks:
• Compression
• Tension
Compression
• Compression occurs when rock is
squeezed.
• Compression happens when two plates
collide at a convergent boundary.
• Compression occurs and forms large
mountain ranges.
Compression/ Mountain Building
The Himalayas, for example, were raised by the compression that
accompanied collision of the Indian plate with the Eurasian plate. Another
example is Europe's Alps and Jura mountains which were also formed by
horizontal compression, generated in their case by collision with the African
plate and the Eurasian plate.
Tension
• Tension occurs when an object is
stretched.
• Tension occurs when plates move away
from each other at plate boundaries
• Example: mid-ocean ridge
Folding
• Folding is the bending of rock layers due
to stress in the Earth’s crust. Caused by
compression.
• Depending on how rock layers deform,
different types of folds occur:
• Anticline
• Syncline
• Monocline
FOLDS
Upward arch
Downward arch
Anticline
• An anticline is an upward-arching fold.
• An anticline is formed when there is
horizontal stress on rock layers.
Horizontal stress
Syncline
• Synclines are downward folds.
• They are also caused by horizontal stress.
Horizontal Stress
Monocline
• Monoclines are rock layers that are folded
so that both ends of the fold are horizontal.
Faults
• Some rock layers break when stress is
applied to them.
• The surface along which rocks break is
called a fault.
• The blocks of crust on each side of the
fault are called fault blocks.
• A fault has a foot wall and a hanging wall.
Footwall
Footwall
You could walk up this face of the fault, on foot, hence the
name footwall.
Hanging Wall
• You could hang from this wall.
Hanging Wall
This is a
normal fault.
Notice how the
rock layers are
the same at
the red lines.
Hanging wall and Footwall
3 Types of Faults
• Normal Fault
• Reverse Fault
• Slip-Strike Fault
Normal Fault
• Rocks are pulled apart because of tension.
Hanging wall
Footwall
In a normal Fault, the hanging wall slides down the
footwall.
Reverse Fault
In a reverse fault the hanging wall is
pushed upward due to compression.
Strike-Slip Fault
Opposing forces cause rocks to
move horizontally. Earthquakes
occur along these faults.
San Andreas Fault, California
Strike-Slip Fault
3 Most Common Types of
Mountains
• Mountains exist because tectonic plates
are continually moving around and
colliding with each other.
• There are 3 types of mountains, named for
how they form:
• Folded Mountains
• Fault-Block Mountain
• Volcanic Mountain
Folded Mountains (Compression)
• Folding is a process in which the Earth's plates are pushed together
in a roller coaster like series of high points and low points.
• Folding bends many layers of rocks without breaking them. The
Appalachian Mountains and Rocky Mountains of the United States,
and the Alps of Europe are examples of mountain ranges that were
formed by folding.
Fault- Block Mountains
(Tension)
• Mountains sometimes form when many layers of the Earth's crust
are moved vertically upward at fault lines by pressures caused by
plates colliding. Fault lines are great cracks in the crust. The
mountains that are formed in this way are called fault-block
mountains. The Sierra Nevada mountains in California and
Nevada, and the Grand Teton range of Wyoming are examples of
fault-block mountains.
Fault block mountains form when
tension causes large blocks of
crust to drop down relative to other
blocks.
Volcanic Mountains
• Volcanic mountains are forms when
magma erupts from a divergent boundary
and hardens.
• Many volcanic mountains exist under the
sea.
• Some volcanic mountains rise above the
surface of the ocean to from islands,
Hawaii for example.
Hawaiian Islands