http://www.geospectra.net/lewis_cl/geology/geo07.jpg
By: Adriana
Montoya
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
Although some
joints occur in
roughly parallel
groups.
http://www.geology.wisc.edu/~maher
/air/122-25v.jpg
http://www.depauw.edu/acad/geoscienc
es/fsoster/W2.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/ge
ology/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.azdot.gov/highways/ima
ges/SuperRedTan.gif
http://www.hku.hk/yscn0007/HKNE%20%20Landscapes%20IV%20(Hong%20Kong%27s%
20landscapes)_files/photo19sm.jpg
http://www.ma.nrcs.usda.go
v/news/images/Tyler_dam.jp
g
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/Colu
mnTops.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/sc
hlphoto/terreco/weathering.jpg