Introduction
Tectonic force are those kinds of forces that originate from beneath the surface and alter the surface configuration of the earth due to lithospheric plate movement. (Marko, 2002)
Plate tectonic movement is the movement of the continental plates. It is believed that the earth was once a continuos land mass that broke into major continents/plates i.e Godownaland and Eurcision. This plates broke into the current six continents and this continents are still in motion. The interior of the earth is very hot and the rocks that are in the interior are in molten form (magma) which is in continuos motion causing earths crust to move.
Stress and Strain
Rocks of the earth are always in motion due to mountain building, continetal drift and seafloor, thus, spreading this results into stress. Stress is a type of pressure that is applied to rock. There are different kinds of stress: lithostatic is the force that its applied evenly on the rock, differential is that force that isn’t evenly distributed. Differential stress is further categorised into tensional, compressional and shearing. On the other hand strain is the pull force that acts on the bedrock. These derformation are further classified into brittle, ductile and elastic.
Joints and Faults
These are both fractures that occur on the bedrock. They are due to stress such as tension compression and torsion. Joints show no displacement of rocks on either side. Faults are planes of displacement. (Ford and Cullingford, 1997) Joints normaly take place in two forms that is conjugate and oblique. Oblique joints which bisect some of the conjugate blocks. Conjugate are regular in occurance and form rectangular ”blocks”. Joints that passes more than one bed are reffered to as master joints.
Fault is simply a line of weakness that is formed from the process of faulting which is the breaking or fructuring of the crystal rocks in the rockbed on the surface of the earth. This fructuring is caused by forces of tension, compression or shear. This forces leads to formation of different types of faults. There are maily three types of faults; normal, reversal and shear.
Normal fault are those forces that act away from each other in the bedrock. Reversal fault is a fault as a result of compressional forces or forces that act towards each other on a bedrock. Shear fault is due to the forces that act paralell to each other. A fault is said to be active if it has moved one or more times from the time it was formed. The genesis of faults may be due to frictional properties, temperature, effective stress normal to the fault.
Uncomformity is always younger than the strata upon which it was developed and older than the overlying strata or features which cut across it. Faulting can take place and with the help of the forces assocciatted, the earth’s crust in an undisturbed state is jeorpadised. Joints will make different blocks to intermingle making the crust to be of different strata.(Florez and Marko, 2002)
References
Florez, J. and Marko, G. Conjugate Faults and Fracture Localization In Brittle rocks: AGU, 2002.
Ford and Cullingford. The science of Speleology. Mcmillan, 1997.