Sharon Johnson GeoImages.Berkeley.EDU.
description
Transcript of Sharon Johnson GeoImages.Berkeley.EDU.
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Sharon Johnson http://GeoImages.Berkeley.EDU.
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 tear down that which is built – e.g. rivers, glaciers and weathering
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Sharon Johnson http://GeoImages.Berkeley.EDU.
Folding, Faulting and Denudation
This unit will examine the “balance” between some localized forces – folding, faulting and denudation (levelling of the surface)
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Sharon Johnson http://GeoImages.Berkeley.EDU.
Folding, Faulting and Denudation
Tectonic activity is an “earth-building” activity
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http://www.geog.ouc.bc.ca/physgeog/contents/10l.html
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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http://volcano.und.nodak.edu/vwdocs/volc_images/
img_arenal1.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)
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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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http://astro.sau.edu/~earth/html/md11.html
Folding
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Folding, Faulting and Denudation
Faults
This is a transform plate boundaries, the most
famous example of which is the San Andreas Fault
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http://astro.sau.edu/~earth/html/md11.html
Folding, Faulting and DenudationOn 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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http://salem.k12.va.us/shs/lester/ch16faulting.html
Folding, Faulting and Denudation
Normal fault – side or profile view
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http://salem.k12.va.us/shs/lester/ch16faulting.html
Folding, Faulting and Denudation
Reverse fault – side or profile view
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http://salem.k12.va.us/shs/lester/ch16faulting.html
Folding, Faulting and Denudation
Strike-slip fault – side and top view
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http://astro.sau.edu/~earth/html/md11.html
Folding, Faulting and DenudationWhere 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 earth’s surface.
Consists of two broad categories :
•degradation (weathering, erosion and transportation)
•aggradation (deposition)
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Lisa Wells http://geogweb.berkeley.edu/GeoIma
ges/Wells/geomorph/adobe.html
Folding, Faulting and DenudationOnce 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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Lisa Wells http://geogweb.berkeley.edu/GeoIma
ges/Wells/geomorph/tufoni1.html
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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http://www.geo.duke.edu/geo41/wea017.gif
Folding, Faulting and Denudation
Mechanical weathering
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http://www.dc.peachnet.edu/~pgore/geology/geo101/weather.htm
Folding, Faulting and Denudation
Chemical weathering
Karst topography
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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 air, water or ice.
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http://maps.unomaha.edu/maher/geo117/part2/masswastingpics/
Svalbardtalus.jpeg
Folding, Faulting and Denudation
Talus slope at base of mountain
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www.ahs.cqu.edu.au/humanities/geography/52120/trial2/
folding&.htm
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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http://www.northernterritory.com/3-2.html
Folding, Faulting and Denudation
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http://www4.vc-net.ne.jp/~klivo/gen/geology.htm
Folding, Faulting and DenudationIn Ontario, the Niagara Escarpment has been formed by
differential erosion.
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http://www4.vc-net.ne.jp/~klivo/gen/geology.htm
Folding, Faulting and Denudation
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http://www4.vc-net.ne.jp/~klivo/gen/nmapeng.gif
Folding, Faulting and Denudation
The escarpment is the exposed edge of a large scale syncline (geosyncline).
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http://www4.vc-net.ne.jp/~klivo/gen/geology.htm
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.