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Obj. 1. Explain transform, divergent and convergent boundaries. 2. Define faults and describe three fault types. II. Plate Boundaries and Faults a) Plate Boundaries – are the point where two tectonic plates meet and are divided into three types – convergent, divergent, and transform. Plates are classified into one of the three types based on the movement that they have. Remember: convection currents are the engines that drive plate movement. 1. Convergent boundary – are the boundaries (edges) that move toward each other or together. When convergent plate boundaries run into each other, three things can occur: a. the plate edges are forced up (creates mountains), b. one plate goes under the other (subduction) (creates earthquakes or volcanoes), c. the plate edges are forced down (creates trenches). 2. Divergent boundary – are the boundaries that move away from each other. The plate edges are pulled apart which causes: a. rift valley – the crust reaches elastic limit and breaks creating two new edges which move away, causing the middle portion to fall, b. depression – the crust stretches but does not reach elastic limit and break, c. ocean ridges – from seafloor spreading. 3. Transform boundary – the edges of the plates move side by side or back and forth to each other. The moving plates cause the crust to break creating friction that makes the rock melt and rock formations to deform which causes: a. volcanoes, and b. earthquakes. e) Faults are the surface along which rocks break and move, rocks on either side of a fault move in different directions relative to the fault surface creating different types of faults. 1. Reverse faults – are caused by convergent plate boundaries and compression forces. The land/plate moves in opposite directions together and gets pushed past its elastic limit causing two things to occur: a. folding-the rocks fold without breaking, b. the rocks break and slide under each other. 2. Normal faults – are caused by divergent plate boundaries and tension forces. The land/plate gets pulled past its elastic limit causing two things to occur: a. rocks break to create a rift valley, b. bends the rocks without breaking to create a depression. 3. Strike-slip faults are caused by transform plate boundaries. The land/plate slips and slides past each other in opposite directions creating friction and vibrations. This fault creates deformation of rocks and many earthquakes in the crust.