Endogenic Processes of the Earth - GEO01 Course Outcome 5 - MAPUA University PDF

Endogenic Processes of the Earth Course Outcome 5 GEO01 – Earth Science Materials Prepared by: Ryo Jerome C. Tuzon, LPT Video Lecture Prepared by: Perseval S. Pineda, LPT Plate Tectonics: The Unifying Theory Plate Tectonics Plate Tectonics – Earth’s surface...

Endogenic Processes of the Earth Course Outcome 5 GEO01 – Earth Science Materials Prepared by: Ryo Jerome C. Tuzon, LPT Video Lecture Prepared by: Perseval S. Pineda, LPT Plate Tectonics: The Unifying Theory Plate Tectonics Plate Tectonics – Earth’s surface is composed of a few large, thick plates that move slowly and change in size Plate boundaries – plates move away, toward, or past each other through intense geologic activity Developed from the Source: W. Hamilton, U.S. continental drift and seafloor Geological Survey spreading hypotheses The Major Plates of the World The Early Case for Continental Drift Puzzle-piece fit of coastlines of Africa and South America has long been known Alfred Wegener – noted South America, Africa, India, Antarctica, and Australia have almost identical late Paleozoic rocks and fossils in early 1900s Glossopteris (plant), Lystrosaurus and Cynognathus (animals) fossils found on all five continents. Mesosaurus (reptile) fossils found in Brazil and South Africa only. Source: C.R. Scotese (www.scotese.com)  Pangaea Pangaea – supercontinent proposed by Wegener Laurasia - northern supercontinent Source: Arthur Holmes, Principles of Physical containing North America and Asia Geology, 2nd ed., Ronald Press, 1965. (excluding India) Gondwanaland - southern supercontinent containing South America, Africa, India, Antarctica, and Australia Late Paleozoic: Glaciation patterns were evident on the southern continents (Gondwanaland) Coal beds deposited in the northern continents from swampy, probably warm environments (Laurasia)  Paleoclimate Belts and Polar Wandering Paleoclimate belts – suggested polar wandering as potential evidence for continental drift. Polar Wandering – the apparent movement of the poles The evidence for this can be explained in three ways: 1) The continents remained motionless and the poles actually moved (polar wandering). 2) The poles did not move and the continents moved (continental drift). 3) Both occurred. Source: A. Wegener, The Origins of Continents and Oceans (19 28), Dover Publications, 1968  Skepticism About Continental Drift Skepticism About Continental Drift Land Bridges – could explain the distribution of land-dwelling reptiles on scattered continents Winds or Oceans currents – could explain distribution of fossil plants on separate continents Polar Wandering – could be explained by moving poles rather than moving continents Mechanism – Wegener’s proposed mechanism was not accepted by most geologists in the northern hemisphere His idea that the continents plowed through the oceans propelled by centrifugal forces from the Earth’s rotation and gravitational forces that cause the tides were proven to be insufficient.  The Revival of Continental Drift Paleomagnetism – the study of ancient magnetic fields The mineral magnetite becomes magnetized in cooling lava once its temperature drops below the Curie Point. Uses mineral magnetic properties to determine direction and distance to the magnetic pole when rocks formed. Steeper dip angles indicate rocks formed closer to the magnetic poles. Rocks with increasing age point to pole locations increasingly far from present magnetic pole positions. Evidence from Paleomagnetism Apparent polar wander curves for different continents suggest real movement relative to one another. Permian rocks in every continent show a different pole position which seems highly unlikely. By reconstructing their locations to form Pangaea, the polar wandering paths are nearly identical indicating that the continents were once joined together.  Geologic Evidence for Continental Drift Fitting of Continents: Redefined the edge of each continent as the middle of the continental slope greatly improved the fit Isotopic ages, glacial striations, rock types, structure and sequence match History of Continental Positions: Rock matches show when the continents were together Paleomagnetic data indicate the direction and rate of movement Pangaea split apart 200 million years ago but the continents have been in motion for much longer (2 to 4 billion years)  Seafloor Spreading Seafloor spreading – the concept that the sea floor is moving like a conveyor belt away from the crest of the mid-oceanic ridge until it disappears by plunging beneath a continent or island arc. Proposed in 1962 by Harry Hess Hess’s Driving Force Deep Mantle Convection – circulation pattern driven by rising of hot material (hot mantle rock) and/or the sinking of cold material (oceanic crust) Seafloor_spreading (viddler.com) Explanations The Mid-Oceanic Ridge Hot mantle rocks rises beneath. Decompression melting occurs. Circulation pattern diverges moving rock away from the ridge. Rift valley forms due to tensional forces at the ridge crest. Oceanic Trenches Rock has cooled and become denser. Crust Sinks beneath a continent or island arc back into the mantle. Age of the Sea Floor Overall young age for sea floor rocks (everywhere 500 km. Typically covered with young sediments. Continental slopes – relatively steep slopes that extend down from the edge of the continental shelf to the abyssal plain. Submarine Canyons Submarine canyons – V-shaped valleys that run across continental shelves and down continental slopes. Deliver continental sediments to abyssal fans on deep sea floor. Turbidity currents – great masses of sediment laden water that flows down the continental slope. Passive Continental Margins Includes a shelf, slope and rise extending down to an abyssal plain. The Continental Rise – gently seaward- sloping (0.5°) wedges of sediments extending from base of continental slope to deep sea floor. Sediment deposited by turbidity and contour currents. End at abyssal plain at depth of about 5 km. Lie upon oceanic crust. Abyssal plains – extremely flat regions beyond the base of the continental rise. Flattest features on Earth, with slopes