Transcript ppt
Extensional margins Intercontinental rift zones Spreading centers Spreading Centers Iceland Oceanic ridges Gulf of Suez Rift Intercontinental rifting Basin and Range Extensional faults in Canyonlands National Park, Utah Analog models of extension QuickTime™ and a Cinepak decompressor are needed to see this picture. Go to movie of our sandbox experiment Analog models of extension Claybox experiments at UMass Investigations with extension experiment in progress at UMass with undergraduates Aims of the investigation: Does the Earth’s crust deform under extension the same as under contraction? Is the pattern of earthquakes the same in extension and contraction? Wasatch Mountains in Utah Questions of investigation: How does topography change during extension? What causes the topography to change? Where are the active faults located? How many faults are active at any time? Activities Observe Sketch <-> observe Label Measure Graph Predict Data Collection # turns (cm) Basin depth (cm) Basin # active faults length (cm) Extensional faults dip different from contraction Shallow faults form during contraction (30˚ dip) Steep faults form during extension (60˚ dip) It is consistent! Extension and contraction are 90˚ apart 30 60 30 60 Effect of Existing faults Cut a fault into the sand pack that might not be oriented as favorably for slip as a new fault. Does the new fault form or old fault reactivate? Hey what about strike slip? Clay shows interesting patterns of echelon cracks Clay cake on top of two boards Pull one board slowly From SERC