  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)