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2/9/2015 Physical Geography The physical landscape (natural environment) sets the stage for human use (cultural landscape). Physical Landscape I of the United States and Canada Prof. Anthony Grande ©AFG 2015 1 2 Physical Geography Definitions Geography: study of people living on the surface of the earth. Geology: the scientific study of the earth and its processes. Geomorphology: the study of landforms and landform regions. Topography: the study of a landform region’s surface features. We need to be aware of its parts and mechanisms. – geologic processes (tectonic/gradational) – atmospheric processes (weather/climate) – water resources (surface/underground) – soils (formation/fertility) – natural vegetation (a result of all of above) 3 4 Shape and Position of the Continents Today Physical Geography For the US&C need to be aware of the role of: 1. Plate Tectonics and Continental Drift and all processes that shape the natural landscape. North America 2. Great Range of Latitude: from polar to topical and its influence on climate formation, vegetation and human response. 3. Climate Change: esp. the continental glaciation associated with the Ice Ages (global cooling) and present trends (global warming). 4. Water: the chief sculptor of landform features and important for well-being of people. 5. Human Impact: effect of people and their works on the natural landscape. Europe Asia Africa South America Australia Antarctica (not shown) 5 How did they get to be shaped and positioned? 6 1 2/9/2015 Plate Tectonics Theory Plate Tectonics Theory The present-day position of the continents is a result of a single land-mass called Pangaea being separated along the lithospheric cracks (plate boundaries) by Dates from the 1960s: • Says the lithosphere (crust + upper mantle) is broken into sections (now called plates), which move relative to each other by forces inside the Earth. • The lithosphere (40-250 mi thick) is rigid. • It’s surface layer (crust) is com The rigidity of the lithosphere posed of an oceanic layer causes it to crack under (denser rocks) and a continental pressure from internal layer (less dense rocks). forces. the movement of convection cells within the mantle. Each segment has slowly been repositioned (shifted). – Movement of the plates continues to occur. 7 8 225 mya Continental Drift Plate Tectonics N. Am. This movement creates: Oldest rock units on today’s continents line up on the map of Pangaea. a. Gaps allowing new crust to form >> spreading zones. b. Forces plates against each other where they collide, override each other and deform >> mountain building. Similar geologic layers and fossil beds on the continents are linked when the continents are brought back to their Pangaea positions. c. Pushes old crust back into the earth >> subduction zones. It is responsible for earthquakes and volcanic activity. This movement created the phenomena that gives us our present-day surface features. N. Am. Note the position of North America on each map. TODAY 9 10 Location of the Earth’s Plates and Directions of Movement Earth’s Surface without Water Note underwater mountain ranges (which mark spreading zones), subduction zones (areas of earthquake and volcanic activity) and the continental shelves (areas flooded by sea level rise). North America Subduction zones (oldest rocks) Spreading zones (youngest rocks) 11 KEY 12 2 2/9/2015 Focus on North America Because of Plate Tectonics… • The North American plate is moving westward and meeting resistance from the Pacific, Juan de Fuca and Cocos plates. – Western North America’s surface features are younger and steeper (angular) than the Eastern North America. – Eastern North America’s features are older and more worn down (rounded). • Earthquakes are more common in the west. • Eruptive volcanic activity is exclusively a western phenomena. • The volcanically-formed Hawaiian Islands are not near a plate boundary but located on a plate that is moving over a “hot spot.” Earthquake Zones The San Andreas fault is the most famous fault line of North America. 14 13 Geologic Map of North America Because of Plate Tectonics… o The eastern coast has a wide, extensive continental shelf and coastal plain. o The western coast has a narrow or non-existent continental shelf and coastal plain. The western coast exhibits relatively few coastal marshes, swamps and barrier islands. The eastern coast has a good supply of each. • The western coast has fewer inlets and estuaries (important as safe, natural anchorages) than the eastern coast. The subsurface 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, including remnant surface features. from the National Atlas of the United States From the National Atlas of the United States 15 Physiographic Diagram of North America The continent’s underlying geologic structure and its dynamic processes of formation and change over the eons have shaped the land surface features of North America. In turn these have influenced running water, soil formation, natural vegetation and human perception. Together they create physiographic regions. 16 Physiographic Regions of the US&C Based on the bedrock geology and the surface geomorphology, we can divide the US&C into distinct physical regions. http://mapmaker.rutgers.edu/355/raisznorthamerica1000.jpeg 17 18 From Birdsall, Regional Landscapes of the US&C 3 2/9/2015 Folding GEOLOGIC PROCESSES TECTONIC (building) GRADATIONAL 1. Folding 1. Mechanical and chemical weathering (in place) 2. Mass wasting (by gravity) 3. Agents of Erosion 2. Faulting 3. Volcanism Folding is the crumpling of the surface upon impact (collision; mountain building). (reducing) (erode → transport → deposit take → NATURAL PROCESSES 1. 2. 3. 4. Mass movements (gravity) Earthquakes (tension release) Volcanism (heat, pressure) Subsidence (sinking) move → place ) Running water Moving ice Wind Wave action Longshore currents 19 Faulting 20 Volcanism Volcanism is when the combination of great pressure and heat is able to melt rock. Release of stress (pressure) is faulting. Earthquakes are a result of the process. Forces at work: movement, tension, shearing, breaking Forces at work: Compression, bending, breaking 21 Forces at work: melting, movement of molten material (oozing), build-up of gasses under pressure (explosion). 22 Steep-sloped rounded peaks Southern Appalachian Mts., NC Topographical Units All the geological processes -- combined with various atmospheric processes -- give us distinct landforms within the physiographic regions: 1. 2. 3. 4. 5. Mountains Plains Hills Plateaus Coastlines (has a relationship to sea level) 23 24 4 2/9/2015 Folded Appalachians Rocky Mts., Banff NP, Alberta in central Pennsylvania 25 Fault Block Topography Basin and Range, Nevada 26 Great Plains North Dakota 27 Colorado Plateau Hill Areas Foothills, Canadian Rockies, Alberta Sand Hills, Nebraska 28 Grand Canyon NP, Arizona Quebec City was built on a hill top Hills of eastern Tennessee 29 30 5 2/9/2015 Pacific Northwest Volcanic Zone West Coast Volcanic Zone Mt. Rainier, WA Mt. Shasta, CA Mt. St. Helens, WA Subduction leads to the formation of volcanoes. (1980 eruption) 31 Hawaii Volcanoes Crater Lake, OR 32 Lava Flows The volcanic activity of Hawaii is related to a “hot spot” not a plate boundary. Kilauea (active) Mauna Loa Lava moving toward the ocean to create new land and changing the Hawaiian coastline. Hawaii’s largest volcano and world’s tallest mountain A black sand beach is created from lava that is quickly cooled as it hits the ocean or wave pulverized basalt (hardened lava) or wave-separated cinders 34 washed ashore. Diamond 33 Head (extinct) Rocky Coast Sandy Coast Maine Northeastern U.S. 35 36 6 2/9/2015 Atlantic Coastal Plain and Barrier Islands Gulf Coast Plain of Texas North Carolina 37 Southern California Coast 38 Central California Coast Rugged, mountain-fringed coastal area of central California at Big Sur south of Monterrey. < Laguna Beach, CA ^Entrance to San Francisco Bay ^ Torrey Pines beach, San Diego ^ La Jolla, CA 39 Pacific Northwest Coastline Oregon Northern California 40 Coasts of Alaska Nome Juneau Anchorage Inland straits of British Columbia Mountains rise out of the sea. There is no coastal plain and beaches are small and inaccessible.41 Katmai NP 42 7 2/9/2015 NEXT PHYSICAL GEOGRAPHY – Glaciation 43 8