Group presentation.pdf

Group 7 presentation ROCKS UNDER DIFFERENT TYPES OF STRESS  Objectives Understand how rocks are deformed by stress and undergo solid deformation Explain how tension, compression, and shear stresses produce geological structures  Wh...

Group 7 presentation ROCKS UNDER DIFFERENT TYPES OF STRESS  Objectives Understand how rocks are deformed by stress and undergo solid deformation Explain how tension, compression, and shear stresses produce geological structures  What is Stress? The force per unit area on a rock. It causes a material to change shape, deformation, or strain. It depends on the type of rock, the surrounding temperature and pressure conditions. Rock's possible responses to stress: Strain A rock's response to stress(deformation) Elastic deformation The rock returns to it's original shape or the deformation is reversible Plastic deformation The rock does not return to it's original shape or the deformation is permanent Compressional Stress Squeezes rock together Happens at convergent plate boundaries Two tectonic plates are plowing in each other Powerful earthquakes Chile: Nazca and South America plate Japan: Eurasian plate and Philippine plates Compressional Stress Rocks deforming plastically crumble in folds The lanforms created are Ocean Trenches & Mountain Ranges Three major types of rock folding: Monoclines Anticlines Synclines Three major types of rock folding: Monocline - is a step-like fold in rock strata consisting of a zone of steeper dip within an othetwise horizontal or gently dipping sequence. Anticline - is a structural trap formed by the folding of rock strata into an arch-like shape. Syncline - are trough-like ( "U" shaped), upward- curving folds with beds that dip towards the fold's central axis. Three major types of Rock folding Monocline Anticline Syncline Tensional Stress Extensional stress Stretches and pulls rocks apart Occurs along divergent plate boundaries Two tectonic plates are tearing from one another. The landforms created are Continental Rifts & Mid-ocean Ridges. Shear Stress When two blocks of rocks are pushing in opposite directions. Causes rock to change shape as they slide against each other. The landforms created are Faults & Fault zone. Shear stress Forces slide past each other in opposite directions. Friction produces the stress. Associated with transform faults or also be called strike-slip or slip-strike fault.  Types of stress Compression: Tension: Shearing: when two plates causes the rocks to pushes some of the collided pull apart crust in different directions SEATWORK