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.