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Transcript
Mountain Building, Earthquakes, and Seafloor Landforms Mountain Building Terms: Ranges linear association of peaks System combination of ranges Mountain Building Mountains form in various ways: Volcanic Due to both convergent and divergent plate boundaries Differential weathering and erosion Erosion of batholiths that are revealed at the surface Block faulting Tensional stress pulls and causes normal faults The uplifted blocks are horsts The down dropped blocks are grabens Mountain Building Orogeny mountain building episodes This occurs at convergent plate boundaries You will see deformed sediments present at a current or historical orogeny Mountain Building Continent – Continent Convergence This happened when the Indian and Eurasian plates collided. Because of this convergence that continues even today the Himalayans are still “growing” There are other convergences that produce orogenies but this is the main one Earthquakes Earthquakes are vibrations of the earth, caused by a sudden release of energy, usually as a result of faulting Magma movement can also trigger earthquakes Usually caused by a transform plate boundary Earthquakes Aftershocks are adjustments along a fault after an earthquake, but still are felt as vibrations This is because of the elastic rebound theory When the strength of rocks is exceeded, the rocks will snap back to their former shape Earthquakes Terms: Seismology the study of earthquakes Seismograph instrument which measures earthquakes Focus location where the earthquake originates Epicenter location on earth’s surface directly above the focus (usually what is mentioned by the media) Earthquakes Seismic Waves Body Waves travel through the Earth P waves Primary waves These are the fastest, and the first detected They act as compressional waves Earthquakes S waves Secondary waves These are shear waves/transform waves, they move perpendicular to line of travel These waves cannot be transmitted through a liquid Earthquakes Surface Waves are waves that travel on the ground Rayleigh waves (R-waves) Slower moving wave Moves similar to water waves (circular) Love waves (L-waves) Lateral motion waves These waves cause damage to the foundations of many buildings Earthquakes Locating You the Earthquake need three locations where P and S waves were measured With those locations circles can be drawn that have radii equal the distance measured from a time-distance graph Earthquakes The intersection of these three circles is the location of the epicenter This needs to be done quickly so the population can be warned about other effects of the earthquake Earthquakes Effects: Ground shaking (most obvious) Ground failure Solifluction and liquefaction Slumping Landslides Fire Tsunamis seismic sea waves Earthquakes Distribution: 80% occur in the circum-Pacific belt, along convergent plate margins 15% occur in the Mediterranean-Asiatic belt 15% are scattered, some occur in plate interiors 1811-1812 New Madrid, MO Failed rift valley Seafloor The Ocean Basins 97.2% of Earth’s water is in the Oceans Pacific Ocean Atlantic Ocean Indian Ocean Arctic Ocean Seas are smaller bodies of water Red Sea Dead Sea Caspian Sea Seafloor Profile: Coast Continental margins Continental shelf Continental slope Continental rise Deep ocean basin Seafloor Continental Margins Types: Active Oceanic plate is subducted beneath continental plate (convergent plate boundary) No continental rise is present There is an oceanic trench though Very narrow continental shelf Lots of volcanoes, earthquakes, and mountains Seafloor Passive Occur within a plate area Broad continental shelves Has both continental slope and rise There is an absence of a trench Seafloor Continental shelf Gentle slope downwards Varies in width Ends at the shelf – slope break Average depth today is 135 m Seafloor Continental slope Steep decline Presence of submarine canyons Sediment is transported by gravity at this point This is a location of turbidity currents/graded bedding Deposits from the turbidity currents and other gravity flows accumulate in submarine fans Seafloor Continental rise Very gentle slope Sediments are transported by gravity This is not present in an active margin In the passive margins, sediments form series of overlapping fans and develops the rise Seafloor Deep Ocean Basin Very dark, cold, intense pressure felt here Abyssal plain Large flat areas Sediments have buried the rugged seafloor Trenches Long, narrow areas Deepest parts of the ocean; associated with volcanoes Oceanic ridges Volcanic rocks (basaltic) Tensional forces/divergent plate boundaries Ridges are often offset by transform faults
