Transcript Folding, Faulting and Denudation

Folding, Faulting and Denudation
Sharon Johnson
http://GeoImages.Berkeley.EDU.
Folding, Faulting and Denudation
Forces in Balance
Some forces build up the earth – e.g. plate tectonics,
volcanoes and folding and faulting.
Other forces tear down that which is built – e.g. rivers,
glaciers and weathering
Folding, Faulting and Denudation
This unit will examine the
“balance” between some
localized forces – folding,
faulting and denudation
(levelling of the surface)
Sharon Johnson
http://GeoImages.Berkeley.EDU.
Folding, Faulting and Denudation
Tectonic activity is an “earth-building” activity
Sharon Johnson
http://GeoImages.Berkeley.EDU.
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
http://www.geog.ouc.bc.ca/physgeog/
contents/10l.html
Folding, Faulting and Denudation
Volcanism is the term
used to describe the
movement of molten
rock beneath or above
the earth’s surface
(covered in another
unit)
http://volcano.und.nodak.edu/vwdocs
/volc_images/img_arenal1.html
Folding, Faulting and Denudation
Folds
Occur when
compressional
forces cause
rock layers to
bend
Folding, Faulting and Denudation
Anticline – upfolds or ridges
Folding, Faulting and Denudation
Syncline – downfolds or valleys
Folding
http://astro.sau.edu/~earth/html/md11
.html
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
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:
http://astro.sau.edu/~earth/html/md11
.html
Folding, Faulting and Denudation
Normal fault – side or profile view
http://salem.k12.va.us/shs/lester/ch16
faulting.html
Folding, Faulting and Denudation
Reverse fault – side or profile view
http://salem.k12.va.us/shs/lester/ch16
faulting.html
Folding, Faulting and Denudation
Strike-slip fault – side and top view
http://salem.k12.va.us/shs/lester/ch16
faulting.html
Folding, Faulting and Denudation
Where a block of earth rides up or down between two
parallel fractures we see grabens and horsts
http://astro.sau.edu/~earth/html/md11
.html
Folding, Faulting and Denudation
Denudation – processes which tend to level the earth’s
surface.
Consists of two broad categories :
•degradation (weathering, erosion and transportation)
•aggradation (deposition)
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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.
Lisa Wells
http://geogweb.berkeley.edu/GeoIma
ges/Wells/geomorph/adobe.html
Folding, Faulting and Denudation
Occasionally, differential erosion creates some
interesting features
Lisa Wells
http://geogweb.berkeley.edu/GeoIma
ges/Wells/geomorph/tufoni1.html
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.
Folding, Faulting and Denudation
Mechanical weathering
http://www.geo.duke.edu/geo41/wea0
17.gif
Folding, Faulting and Denudation
Chemical
weathering
Karst topography
http://www.dc.peachnet.edu/~pgore/g
eology/geo101/weather.htm
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 air, water or ice.
Folding, Faulting and Denudation
Talus slope at
base of
mountain
http://maps.unomaha.edu/maher/geo1
17/part2/masswastingpics/Svalbardtal
us.jpeg
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)
www.ahs.cqu.edu.au/humanities/geog
raphy/52120/trial2/folding&.htm
Folding, Faulting and Denudation
http://www.northernterritory.com/32.html
Folding, Faulting and Denudation
In Ontario, the Niagara Escarpment has been formed by
differential erosion.
http://www4.vcnet.ne.jp/~klivo/gen/geology.htm
Folding, Faulting and Denudation
http://www4.vcnet.ne.jp/~klivo/gen/geology.htm
Folding, Faulting and Denudation
The escarpment is the exposed edge of a large scale
syncline (geosyncline).
http://www4.vcnet.ne.jp/~klivo/gen/nmapeng.gif
Folding, Faulting and Denudation
The escarpment is the exposed edge of a large scale
syncline (geosyncline).
http://www4.vcnet.ne.jp/~klivo/gen/geology.htm
Folding, Faulting and Denudation
Where rivers cross the escarpment, waterfalls may be
formed by undercutting.
Folding, Faulting and Denudation
Some of these waterfalls are quite spectacular.