by: adriana montoya
Post on 23-Feb-2016
50 Views
Preview:
DESCRIPTION
TRANSCRIPT
By: Adriana Montoya
Joints
http://www.geospectra.net/lewis_cl/geology/geo07.jpg
JOINTS AND ITS MEANING…
Joints are fractures along which no appreciable displacement has occurred.
Most common rock structures are fractures called joints.
http://nvcc.edu/home/cbentley/geoblog/uploaded_images/columnar_layers-703634.jpg
Joints continued…Parallel group
joints
http://www.depauw.edu/acad/geosciences/fsoster/W2.jpg
Although some joints occur in roughly parallel groups.
http://www.geology.wisc.edu/~maher/air/122-25v.jpg
Columnar Joints Columnar joints
are joints that form when igneous rocks cool and develop shrinkage fractures that produce elongated, pillar like columns. http://www.answersincreation.org/
curriculum/geology/images/columnar_joint.jpg
How joints are produced? Most Joints are produced when rocks in the outermost crust are
deformed. Tensional and shearing stresses associated with crustal movements
cause the rock to fail by brittle fracture. Extensive joint patterns can also develop in response to relatively
subtle and barely perceptible regional up warping and down warping of the crust.
Although jointed rocks present a risk to the construction of engineering projects.
For example, highways, and dams.
http://www.hku.hk/yscn0007/HKNE%20-%20Landscapes%20IV%20(Hong%20Kong%27s%20landscapes)_files/photo19sm.jpg
http://www.ma.nrcs.usda.gov/news/images/Tyler_dam.jpg
http://www.azdot.gov/highways/images/SuperRedTan.gif
Chemical Weathering
Many rocks are broken by two or even three sets of intersecting joints that slice the rock into numerous regularly shaped blocks.
http://www.rbnc.org/schoolunits/schlphoto/terreco/weathering.jpg
http://people.usd.edu/~Brennan.Jordan/ColumnTops.jpg
•Chemical Weathering tends to be concentrated along joints, and in many areas groundwater movement and the resulting dissolution in soluble rocks is controlled by joint pattern.
top related