The and the poisson effects are the
The tensile strength of a large rock sample issignificantly less than that of a small rock sample of the same rock.10. Why are large sample rocks weaker than smallsamples of the same rock? d.
Fracturesdisplay loss of cohesion while most deformation bands retain cohesion or arestronger than the host rock.c. Deformation bandsdo not accumulate more than a centimetre-scale offset while fractures showmeter scale offsets or more.b. Deformationsare thicker than fractures.
a. Deformationsare tabular discontinuities while fractures are sharp discontinuities.9. What is the difference between fractures anddeformation bands? It increases because it is very difficult tofracture a rock under confinement than an unconfined rock. The deeper down inthe upper crust, the more stress that builds up before it fractures. Therefore,the strength increases downwards through the brittle crust, untilcrystal-plastic mechanisms begin at the brittle-plastic transition.8.
Why does the differential stress increasedownwards in the brittle crust? The effective stress will be reduced becausean increased fluid pressure will help in lifting the overburden so that thestress across grain contacts become smaller.7. If we increase the fluid pressure in asandstone unit, will the effective stress increase or decrease? Silica is a more brittlesubstance than shale. It requires much higher energy conditions (highertemperature and pressure) to make silica behave plastically than it does forclay.6. Why does sandstone fracture moreeasily than shale when uplifted? Shear stressTensional stressCompressional stressConfining stress5.
What factor related to platetectonics can cause tectonic stress? It is the movement oftectonic plates (stress) which leads to the formation of a fault in the earthscrust which occurs as a brittle response to stress.4. How can we define tectonic stress? the thermal and thepoisson effects are the two factors. They tend to reduce the horizontal stress.The thermal effect leads to the cooling of rocks as they ascend.
Cooling isresponsible for the contraction and potential fracture of the rock.3. What physical factors controls thestate of stress in a rock that is being uplifted through the upper crust? Experimental dataConventional field workSeismic dataRemote sensing2.
List and explain the major methodsfor collecting structural data sets. They do this throughremote sensing, field work, physical experiments and numerical methods. I wouldrank them based on my interest and the experiment, or even according to theorder given above. Field work will be the first because everything shouldrelate to field studies.
1. Name the four principal ways astructural geologist can learn about structural geology and rock deformation.How would you rank them? ASSIGNMENT