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Folding and Faulting


Folding and Faulting By: Justin Noftall Folds A fold is when the earth s crust is pushed up from its sides. There are six types of folds that may occur: Anticline ... – PowerPoint PPT presentation

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Title: Folding and Faulting

Folding and Faulting
  • By Justin Noftall

  • A fold is when the earths crust is pushed up
    from its sides. There are six types of folds
    that may occur
  • Anticline
  • Syncline
  • Tight Fold
  • Overfold
  • Recumbent Fold
  • Nappe Fold

  • An anticline occurs when a tectonic plate is
    compressed by movement of other plates. This
    causes the center of the compressed plate to bend
    in an upwards motion.
  • Fold mountains are formed when the crust is
    pushed up as tectonic plates collide. When
    formed, these mountains are usually enormous like
    the newly formed Rocky Mountains in Western
    Canada and the United States
  • To the top right is a picture of an anticline.
    Beneath is a picture of the Rocky Mountains.

  • A syncline is similar to an anticline, in that it
    is formed by the compression of a tectonic plate.
    However, a syncline occurs when the plate bends
    in a downward motion.
  • The lowest part of the syncline is known as the
  • To the top right is a diagram of a syncline fold
    (The bottom of the fold center is the trough).
    Beneath, is an example of a syncline in
    California. Can you distinguish the trough in
    this picture?

Tight Fold
  • A tight fold is a sharp peaked anticline or
  • It is just a regular anticline or syncline, but
    was compressed with a greater force causing the
    angle to be much smaller.
  • Folds such as these occur to form steep mountain
    slopes like those in Whistler, British Columbia.
  • To the left is a photo of a tight fold formed by
    extreme pressure on these rocks.

  • An overfold takes place when folding rock becomes
    bent or warped.
  • Sometimes the folds can become so disfigured that
    they may even overlap each other.
  • An example of overfolding is shown in the diagram

Recumbent Fold
  • This type of fold is compressed so much that it
    is no longer vertical.
  • There is a large extent of overlapping and it can
    take the form of an s.
  • To the right is a diagram that shows the process
    of recumbent folding.

Nappe Folding
  • This fold is similar to a recumbent fold because
    of the extent of folding and overlapping.
    However, nappe folding becomes so overturned that
    rock layers become fractured.
  • To the right is a picture of someone standing
    under a fractured fold.

  • A fault is when tension and compression
    associated with plate movement is so great that
    blocks of rock fracture or break apart. This
    process can occur very rapidly, in the form of
    earthquakes. The damage caused by this event can
    be very destructive and cause severe changes to
    the earths surface. There are five types of
    faults that can occur
  • Normal Fault
  • Reverse Fault
  • Tear Fault
  • Rift Valley
  • Horst Fault

Normal Fault
  • This occurs when rocks move away from each other
    due to the land moving apart.
  • When the rocks move apart, the side with the less
    stable tectonic plate drops below the side with
    the more stable plate.
  • On the top right is the movement of a normal
    fault. A picture is also shown below. Notice
    the displacement of the different types of rock
    on each side of the fault.

Reverse Fault
  • Reverse faults are the opposite of normal faults.
    Rocks are compressed such that one plate moves
    up while the other descends below it.
  • When plates compress and crack, usually the more
    dense one is forced under the less dense one.
    This is similar to the action of the continental
    crust colliding with the oceanic crust. Here the
    more dense crust, being the oceanic crust is
    forced under the continental crust.
  • To the right is an animation of a reverse fault.
    Below that is a real picture of what a reverse
    fault looks like.

Tear Fault
  • A tear fault, also known as a transform fault,
    occurs when two tectonic plates slide in a
    lateral motion past each other.
  • This type of fault causes the most severe
    earthquakes because they grind against each
    other. These earthquakes can either be shallow
    or deep and cause tremors over a short or long
    period of time.
  • Tear faults can occur frequently, especially
    along the coast of California.

Rift Valley
  • A rift valley is when two normal faults occur
    parallel to each other and the land sinks between
    the faults.
  • There are two major examples of this. One being
    the Great Rift Valley in North Africa and the
    other, the San Andreas Fault in California.
  • The top right picture is San Andreas Fault and on
    the bottom right is a diagram of what a rift
    valley looks like.

Horst Fault
  • A Horst is the opposite of a rift valley. The
    land between the parallel faults is forced upward
    because the two faults are being pushed together.
  • This process can take a long time to occur
    because the average plate movement is one inch
    per year.
  • There are examples of horst faults on the left.

  • Folding and faulting has a major influence on the
    way the earth looks. Mountains form and disappear
    over time, as well as large rift valleys and
    other features. This has an impact on where and
    how we live.

The End
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