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Plate Tectonics SOL # 8 Physiographic Features in VA • 5 regions • • • • • Costal plain Piedmont Blue Ridge Valley and Ridge Appalachian Plateau Piedmont Appalachian Plateau Blue Ridge Valley & Ridge Coastal Plain Coastal Plain • Flat • Young sediment from Appalachian Mts. Piedmont • Rolling hills • Ancient igneous & metamorphic rocks Blue Ridge • High ridge • Billion year old igneous & metamorphic rocks (oldest in state) Valley & Ridge • Long, parallel ridges/valleys • Folded and faulted sedimentary rocks • Occurred when Africa hit N. America • Happened late Paleozoic era • Made Appalachian Mts. Appalachian Plateau • Rugged, irregular • Coal Geological Processes • Weathering: break down of rocks • Erosion: moving of broke-down sediments • Deposition: putting sediments down after moving • All 3 are interrelated Geological Processes • Folding:compressing rocks horizontally, creating wave-like forms • Faulting:break or crack in the crust from movement Plates • Crust divided into pieces (lithosphere) • “Float” on asthenosphere (upper mantel) • Most geological activity occurs because of plate movement » Earthquakes » Volcanoes » Mountain building 2 Types of Crust • Oceanic • Thin, young, dense • Continental • Thick, old, less dense Plate Boundaries • Convergent: • 2 plates colliding • Results in: • Folded/faulted mountains • Subduction zones (volcanoes/trenches) Plate Boundaries • Divergent: • 2 plates dividing (going apart) • Results in: • mid-ocean ridges • Rift valleys Plate Boundaries • Transform: • 2 plates sliding past one another • Results in: • Strike/slip faults Subduction Zone • When oceanic plate collides with continental plate – Young, dense ocean plate goes under old, less dense continental plate Seafloor Spreading • New seafloor is constantly being made • AKA: Oceanic Crust • Occurs at mid-ocean ridge • Old floor moves away, new floor is close to ridge Continental Drift • Hypothesis stating continents are moving • Once all continents were together as 1: Pangaea • Evidence: • Same reptile fossils found in Africa and S. America • Same plant fossils found Africa, Australia, India, S. America, & Antarctica • Similar rock structures are found on different continents
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