sharon johnson . folding, faulting and denudation

Sharon Johnson http://GeoImages.Berkeley.EDU.

Folding, Faulting and Denudation

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

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)

Sharon Johnson http://GeoImages.Berkeley.EDU.

Folding, Faulting and Denudation

Tectonic activity is an “earth-building” activity

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

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)

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

http://astro.sau.edu/~earth/html/md11.html

Folding

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

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:

http://salem.k12.va.us/shs/lester/ch16faulting.html

Folding, Faulting and Denudation

Normal fault – side or profile view

http://salem.k12.va.us/shs/lester/ch16faulting.html

Folding, Faulting and Denudation

Reverse fault – side or profile view

http://salem.k12.va.us/shs/lester/ch16faulting.html

Folding, Faulting and Denudation

Strike-slip fault – side and top view

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

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)

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.

Lisa Wells http://geogweb.berkeley.edu/GeoIma

ges/Wells/geomorph/tufoni1.html

Folding, Faulting and Denudation

Occasionally, differential erosion creates some interesting features

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.

http://www.geo.duke.edu/geo41/wea017.gif

Folding, Faulting and Denudation

Mechanical weathering

http://www.dc.peachnet.edu/~pgore/geology/geo101/weather.htm

Folding, Faulting and Denudation

Chemical weathering

Karst topography

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.

http://maps.unomaha.edu/maher/geo117/part2/masswastingpics/

Svalbardtalus.jpeg

Folding, Faulting and Denudation

Talus slope at base of mountain

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)

http://www.northernterritory.com/3-2.html

Folding, Faulting and Denudation

http://www4.vc-net.ne.jp/~klivo/gen/geology.htm

Folding, Faulting and DenudationIn Ontario, the Niagara Escarpment has been formed by

differential erosion.

http://www4.vc-net.ne.jp/~klivo/gen/geology.htm

Folding, Faulting and Denudation

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).

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).

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.