Folding, Faulting and Denudation
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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 http://salem.k12.va.us/shs/lester/ch16 faulting.html Folding, Faulting and Denudation Reverse fault http://salem.k12.va.us/shs/lester/ch16 faulting.html Folding, Faulting and Denudation Strike-slip fault 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) 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. 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 (China) 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.
