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Exam 3 - Exam 3 Earth’s Interior Exam – December 14th...

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Unformatted text preview: Exam 3 Earth’s Interior Exam – December 14th Crustal Deformation • Deepest mines in the world o As humans how deep can you go into the earth? o South Africa Gold Mine Tau Tona 3.9 km into the earth Average temperature of 58C • Deeper you go higher the temperature o Mariana Trench 11km deep in ocean Challenger deep – lowest point you can get on the planet • Right now Mariana Trench o Kola institute drill-hole 12 km But only a drill, no people go down there o High Pressures, Low temperatures, focus on gravity No caves – pressure is trying to pack everything together and gravity pulls it to the smaller There are no open spaces deep in the earth Open caves are only in the first couple of km from the earths surface • Deformation o All changes in the original form and/or size of a rock body Study of geology structures • Forces developing within the earth shape the surface • Can’t see deep into the world, so you look at the surface to see what it can tell you about the earths interior o Involves: Force- That which tends to put stationary objects in motion or changes in motions of moving objects Stress- Compressional, tension, shear o Strain – “another word for deformation” Type of deformation that changes in the shape or size of a rock body caused by stress Strain occurs when rocks subject to stresses greater than their own strength begin to deform by folding, flowing, or fracturing Elastic strain deformation • Rock returns to nearly its original size and shape when the stress is removed o Once the elastic limit (strength) of a rock is surpassed, it either flows (ductile deformation) or fractures (brittle deformation) • Ductile deformation – bending of candy cane while it is at a higher temperature - flows • Brittle – breaking candy cane – folds, breaks, fractures - faults • Factors influencing deformation o Temperature High temperature ductile deformation o Confining pressure High pressure ductile deformation o Rock type Eg, shale folds, sandstone breaks o Time Long time to apply stress ductile deformation • Types of stress o Compression Moving into each other - shortens Can see stress, See deformation o Tension (extension) Moving away from each other - lengths Don’t see stress, See deformation o Shear Along fault zones, sliding – slippage Don’t see stress, See deformation • Folds – forces by compression o During crustal deformation rocks are often bent into a series of wave-like undulations o Most folds result from compression stresses that shorten and thicken the crust o Parts: Limbs – two sides of the folds Axis – line drawn down the points of maximum curvature of each layer Axial plane – imaginary surface that divides a fold symmetrically Plunge – point where the fold disappears, end of a fold • Plunging anticline – 2 ridges or valleys drawn towards the axial plane and they meet...
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Exam 3 - Exam 3 Earth’s Interior Exam – December 14th...

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