By: Adriana Montoya

1. Joints By: Adriana Montoya http://www.geospectra.net/lewis_cl/geology/geo07.jpg

2. Joints are fractures along which no appreciable displacement has occurred. Most common rock structures are fractures called joints. Joints and its meaning… http://nvcc.edu/home/cbentley/geoblog/uploaded_ images/columnar_layers-703634.jpg

3. Joints continued… • Although some joints occur in roughly parallel groups. • Parallel group joints http://www.geology.wisc.edu/~maher/air/122-25v.jpg http://www.depauw.edu/acad/geoscienc es/fsoster/W2.jpg

4. 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

5. 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.ma.nrcs.usda.gov/news/images/Tyler_dam.jpg http://www.azdot.gov/highways/images/SuperRedTan.gif http://www.hku.hk/yscn0007/HKNE%20-%20Landscapes%20IV%20(Hong%20Kong%27s%20landscapes)_files/photo19sm.jpg

6. 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://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. http://www.rbnc.org/schoolunits/schlphoto/terreco/weathering.jpg