Folding, Faulting and Denudation

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Folding, Faulting and Denudation
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Folding, Faulting and Denudation

Forces in Balance  Some forces build up the earth
e.g. plate tectonics, volcanoes, and folding
and faulting. Other forces wear down that which
is built e.g. rivers, wind, glaciers, and
weathering
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Folding, Faulting and Denudation

This unit examines the balance between these
forces.
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Folding, Faulting and Denudation
Tectonic activity is an earth-building activity

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Folding, Faulting and Denudation
Folding is the process that bends and twists
rocks, usually due to compression  Faulting is
the process where rocks move past each other
along a fracture

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Folding, Faulting and Denudation
Volcanism is the term used to describe the
movement of molten rock beneath or above the
earths surface

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Folding, Faulting and Denudation
Folds Occur when compressional forces cause rock
layers to bend

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Folding, Faulting and Denudation

Anticline upfolds or ridges
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Folding, Faulting and Denudation
Syncline downfolds or valleys

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Folding

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Folding, Faulting and Denudation
Faults In the unit on plate tectonics you
discovered the existence of transform plate
boundaries, the most famous example of which is
the San Andreas Fault

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Folding, Faulting and Denudation
On a smaller scale there are a number of other
types of faults, categorized by the relative
motion of the blocks of earth

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Folding, Faulting and Denudation
Normal fault

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Folding, Faulting and Denudation
Reverse fault

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Folding, Faulting and Denudation
Strike-slip fault

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Folding, Faulting and Denudation
Where a block of earth rides up or down between
two parallel fractures we see grabens and horsts

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Folding, Faulting and Denudation

• Denudation processes which tend to level the
  earths surface.
• Consists of two broad categories
• degradation (weathering, erosion, and
  transportation)
• aggradation (deposition)

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Folding, Faulting and Denudation
Once new landforms are created by tectonic
forces, weathering and erosion begin to wear away
at those forms. The overall effect is a
softening of landscapes.

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Folding, Faulting and Denudation
Occasionally, differential erosion creates some
interesting features

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Folding, Faulting and Denudation
Chemical weathering involves a chemical change
in at least some of the minerals within a rock.
Mechanical weathering involves physically
breaking rocks into fragments without changing
the chemical make-up of the minerals within it.

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Folding, Faulting and Denudation
Mechanical weathering

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Folding, Faulting and Denudation

Chemical weathering Karst topography (China)
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Folding, Faulting and Denudation
As soon as a rock particle (loosened by one of
the two weathering processes) moves, we call it
erosion or mass wasting. Mass wasting is simply
movement down slope due to gravity. Rock falls,
slumps, and debris flows are all examples of mass
wasting. We call it erosion if the rock particle
is moved by some flowing agent such as wind,
water or ice.

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Folding, Faulting and Denudation
Talus slope at base of mountain is an example of
mass wasting

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Folding, Faulting and Denudation
Consider this famous landform feature resulting
from a resistant layer of rock appearing at the
surface, surrounded by softer rocks. (Ayers Rock)

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Folding, Faulting and Denudation

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Folding, Faulting and Denudation
In Ontario, the Niagara Escarpment has been
formed by differential erosion.

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Folding, Faulting and Denudation

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Folding, Faulting and Denudation
The escarpment is the exposed edge of a large
scale syncline (geosyncline).

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Folding, Faulting and Denudation
The escarpment is the exposed edge of a large
scale syncline (geosyncline).

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Folding, Faulting and Denudation
Where rivers cross the escarpment, waterfalls may
be formed by undercutting.

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Folding, Faulting and Denudation
Some of these waterfalls are quite spectacular.