2/14/2013 Physical Geography Physical Geography I The physical landscape (natural environment) sets the of the stage for human use (cultural landscape). We need to be aware of: United States – geologic processes (tectonic/gradational) and Canada – atmospheric processes (weather/climate) Prof. Anthony Grande – water resources (surface/underground) ©AFG 2013 – soils (formation/fertility) – natural vegetation (a result of all of above) 1 2 Physical Geography Physical Geography We need to be aware of the role of: The region’s physical characteristics affect: • Plate tectonics and continental drift as well as • The continent’s political boundaries the various processes that shape the natural landscape. • Population growth and movements • The great range of latitude – the Tropics to the • Technological innovation Arctic - and its influence on climate formation. • Climate change, especially past continental glacia- • Urban growth and sprawl tion associated with the Ice Ages (global cooling) and • Resource use and misuse global warming (present) for the future conditions. • Food production • Water as the chief sculptor of landform features, and • Industrialization and de-industrialization for the location, movement and well-being of people. • Human impact on the natural landscape - people and their works. 3 4 Definitions Current Position of the Continents Geography: study of people living on the surface of the earth. North Europe Geology: the scientific study of the earth and its America Asia processes. Africa Geomorphology: the study of landforms. South America Topography: the study of surface features of the Australia Antarctica landforms. (not shown) 5 6 1 2/14/2013 Cross-section of the Earth Plate Tectonics Theory Earth’s interior is • Dates from the 1960s: postulated that the extremely hot and Earth’s lithosphere (crust +upper mantle) is broken into exerts great pressure sections now called plates, which move (not drift) on the lithosphere, relative to each other by forces in the Earth’s causing the crust interior. (which covers it) to crack and break into • The lithosphere is rigid. large units called • It is composed of an oceanic crust of denser plates. rocks and a continental crust of less dense rocks. • The rigidity of the lithosphere causes it to crack 7 under pressure from internal forces. 8 Plate Tectonics Theory Continental Drift 225 mya • The present day position of the continents is a result of a single huge landmass (Pangaea) being separated along the cracks (plate boundaries) and each segment being slowly repositioned (shifted). • Movement of the plates continues to occur. TODAY Oldest rock units on today’s continents line up on the map of Pangaea. 9 10 Earth’s Surface without Water Plate Tectonics Theory showing features associated with plate boundaries • This movement creates gaps in the lithosphere allowing new crust to form: spreading zones. • This movement also forces plates against each other where they collide, override each other and dfdeform. Subduction • Eventually, old crust returns to the earth’s interior: zones (oldest subduction zones. rocks) • This movement creates the phenomena that gives give us our present-day surface features. Spreading zones (youngest rocks) • This movement results in earthquakes and volcanic eruptions. 11 12 2 2/14/2013 Folding Faulting Folding is the crumpling of the surface upon impact Release of stress (pressure) is faulting. (collision; mountain building). Earthquakes are a result of the process. Forces at work: Compression, bending, breaking Forces at work: movement, tension, shearing, breaking 13 14 Volcanism Location of the Earth’s Plates Volcanism is when the combination of great pressure and their directions of movement and heat is able to melt rock. Forces at work: melting, movement of molten material 15 16 (oozing), build-up of gasses under pressure (explosion). The San Andreas fault is the most famous fault line of North America. Plate Tectonics and North America Plate Tectonics and North America • The North American plate is moving toward • The western coast has little or no coastal the west and meeting resistance from the plain while the eastern coast has a wide Pacific, Juan de Fuca and Cocos plates. extensive coastal plain. • Western North America’s surface features • The western coast exhibits relatively few are younger and steeper (angular) than the coastal marshes, swamps and barrier Eastern North America. islands, while the eastern coast has a good • Eastern North America’s features are older supply of each. and more worn down (rounded). • The western coast has fewer inlets and • Earthquakes are more common in the west. estuaries (important as safe, natural anchorages) • Today, volcanic activity is exclusively a western than the eastern coast. phenomena. 17 18 3 2/14/2013 Geologic Map Physiographic Regions of of North America North America The geology of North America is varied and very complex. The continent’s paleogeography has changed many times. This can be seen in its rock record. from the National Atlas of the United States http://rst.gsfc.nasa.gov/Front/tofc.html 19 20 Physiographic Regions Physiographic Regions of the Conterminous U.S. (lower 48 states) 21 22 Physiographic Regions GEOLOGIC PROCESSES of Canada TECTONIC (building) GRADATIONAL 1. Folding 1. Mechanical and chemical 2. Faulting weathering (in place) 3. Volcanism 2. Mass wasting (by gravity) 3. Agents of Erosion (erode → transport → deposit) NATURAL PROCESSES (take → move → place ) 1. Mass movements (gravity) . Running water 2. Earthquakes (tension release) . Moving ice . Wind 3. Volcanism (heat, pressure) . Wave action 4. Subsidence (sinking) . Longshore currents 23 24 4 2/14/2013 Topographical Units Rocky Mts., Banff NP, Alberta All the geological processes, combined with various atmospheric processes, give us landforms within physiographic regions: 1. Mountains 2. Plains 3. Hills 4. Plateaus 5. Coastlines 25 26 Great Plains, North Dakota Hilly Areas Foothills,Canadian Rockies, Quebec City was built on a hill top Alberta Sand Hills, Nebraska Hills of eastern Tennessee 27 28 Colorado Plateau Fault-block Mountains and Grand Canyon NP, Arizona Associated Features 29 30 5 2/14/2013 Basin and Range, Nevada Folded Mountains In folding, lateral tectonic forces cause the outer layers of the lithosphere to compress and form a 31 wave-like surface (“folded mountains”). 32 Rounded peaks of the Folded Appalachians Southern Appalachian Mts., NC in central Pennsylvania 33 34 Locations of historically Volcanism and Subduction Zones recent Volcanic Activity Subduction is a tectonic process in which one plate is overridden by another. 35 36 6 2/14/2013 Pacific Northwest Volcanic Zone Mt. Saint Helens, WA (eruption of 1980) 37 38 West Coast Volcanic Zone Hawaii Volcanoes The volcanic activity of Hawaii is related to a “hot spot” not a plate boundary. Mt. Rainier, WA Mt. Shasta, CA Kilauea (active) Diamond Head (extinct) 39 40 Crater Lake, OR Geography of Earthquakes Rocky Coast Maine Purple dots shows epicenters of major quakes. (Note the relationship to plate boundaries.) 41 42 7 2/14/2013 Coastal Plain and Barrier Islands Sandy Coast North Carolina Northeastern U.S. 43 44 Coastal Plain Coastal Plain of Texas South Carolina 45 46 Central California Coast Pacific Northwest Coastline <<Rugged, mountain-fringed coastal area of central California at Big Sur south Oregon of Monterrey. Northern California ^^Entrance to San Francisco Bay 47 48 8 2/14/2013 Ports of California Coast of Alaska Port of Los Angeles / Ports within San Nome Long Beach (man-made) Francisco Bay (natural) Katmai NP Anchorage 49 Juneau 50 9.