Presentation on theme: " Deformation : changes in the original form and/or size of a rock body Crucial deformation occurs along plate margins Factors that influence rock."— Presentation transcript:
Deformation : changes in the original form and/or size of a rock body Crucial deformation occurs along plate margins Factors that influence rock strength: Temperature, confining pressure, rock type, time Folds : rocks bent into series of waves Almost always associated with underlying faults Most result from compressional forces Which shorten and thicken the crust 70 mya: Laramide Orogeny Laramide Orogeny Activated an ancient fault Overlying rock layers draped above fault Waterpocket fold formed in Capitol Reef NP Waterpocket fold Monocline : regional fold with one steep side West side lifted 7 k-ft above east side 1 6: Deformation and Folds Google Images: Waterpocket Fold
Anticline: upfolded or arched rock layers Syncline: downfolded rock layers Anticlines and syncline s can be: Symmetrical – limbs are mirror images Asymmetrical – limbs re not mirror images Overturned – one limb is tilted beyond vertical Plunging : where folds die out Ex. Sidling Hill Syncline on I-68 Maryland 2 Synclines and Anticlines
Mountain system in eastern North America. Formed during Taconic Orogeny. Formed 480 million years ago during Ordovician. Once as high as the Rockies, now eroded. Contain belts of folded and faulted marine rock. Contains volcanic rock and ancient sea floor. Evidence of continental collision during formation. Mountain-building due to Pangea formation. North America and Africa were connected. Coastal sea coves contain pillow lavas. Evidence of volcanic activity during convergence. Volcanic necks left from past volcanic activity. Original volcanoes eroded during Mesozoic. Cenozoic uplift caused stream erosion. Image of Appalachians near the Blue Ridge Parkway by National Park Service 3 Appalachian Mountains
Mountains have buoyant roots into mantlebuoyant roots Roots 5.6 times deeper than mountain height Mountain roots confirmed by gravity data Deficit in measurement, i.e. missing mass Missing mass must be beneath the mountains Isostasy: crust floating in gravitational balance Isostasy Crustal uplift occurs when weight removed Process is called isostatic adjustment Fig. A: thick continental crust Fig. B : erosion lowers mountains, reduced load Fig. C: erosion and uplift Until mountain reaches normal thickness 4 Buoyancy and Isostasy
Flow from high to low pressure Flow path is called pressure gradient Pressure gradient creates winds Low pressure zone : air rises, cools, forms clouds Produces precipitation High pressure zone: Air descends, flows over ground Creates dry conditions Earth’s rotation: deflects paths of large air Moves water masses Northern hemisphere : moving masses pushed right Southern hemisphere : moving masses pushed left Air Masses Google Images, Air Mass What are air masses, (4:36)
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