Continental Margins Continental shelf: shallowest part of the margin Continental Slope: a steeper part Continental Rise: gently sloping region at the base of the of the continental slope; consists of sediment that piles up on the sea floor

Deep Sea Basins Abyssal plain: flat area Seamounts: old volcanos and islands Trenches: deepest part of the ocean Mid Oceanic Ridge: main feature of the ocean floor Central Rift Valley: great gap at the center where plates are pulling apart

Structure of Earth Earth Originated 4.5 billion years ago by the Big Bang Earth’s materials were sorted by density Densest is found at the center and the least on the outside

Structure of Earth Internal Structure Inner Core: composed of Fe Ni, high pressure and temperatures reach 5,000oC; solid in nature Outer Core: Same elements and temperature but less pressure so is a liquid Mantle: Contains Si and O, semi-solid state that moves like molasses Asthenoshere-upper mantle Crust: outermost layer, extremely thin, rigid skin floating on the mantle (Oceanic and Continental) Lithosphere-uppermost mantle and crust

Earth’s Crust Oceanic Crust Continental Crust Consist of Basalt 200 myo Dense and thin Continental Crust Consist of granite 3.8 byo Not dense and thick

Continental Drift Proposed in 1920 by Alfred Wegener Theory: states that all the continents had once been joined in a single super continent called Pangaea, 180 mya Wegener was laughed at due his inability to proposed a mechanism for the movement of continents

Continental Drift Evidence Coal deposits geological formations fossils match up on opposite sides of the Atlantic Jigsaw puzzle like appearance of continents Glacial rock deposits Limestone and salt deposits

Seafloor Spreading Evidence Discovery of the Mid Ocean Ridge Discovered using sonar Interrupted by large geological fault called transform faults EX: Mid-Atlantic Ridge and East Pacific Rise

Seafloor Spreading Evidence Magnetic Reversals Discovered by the Glomar Challenger in 1968 Symmetric Pattern of Magnetic Bands in the seafloor from reversals of the magnetic poles Opposite matching bands on either side of mid-oceanic ridge

Seafloor Spreading Evidence Sediment Age and thickness Discovered by the Glomar Challenger Thickest and oldest sediments are found farthest from the Mid Ocean Ridge

Seafloor Spreading Proposed by Henry Hess in 1960’s Theory: states that mantle rises up at the Mid Ocean Ridges is then cooled, placed on the seafloor and moved towards the continents Mechanism was thought to be convection of the mantle beneath the seafloor

Plate Tectonics Combination of Continental Drift and Seafloor Spreading Theory: earth’s surface is covered by a fairly rigid layer composed of the crust and the uppermost part of the mantle called the lithosphere that is broken into plates which move over the mantle

Plate Collisions Oceanic Plate to Oceanic Plate Causes trenches, earthquakes, volcanoes and island arcs EX: Aleutian Island in Alaska

Plate Collisions Oceanic Plate and Continental Plate Creates a trench, earthquakes, continental volcanoes Seafloor is destroyed at the trench which explains why the seafloor is so young

Plate Collisions Continental Plate and Continental Plate Create mountains EX: Himalayan Mountains

Plate Movements Apart: plates do move apart and create new crust EX: mid ocean ridge and Iceland Shear Boundary: plate are able to slide past each other EX: California’s San Andreas Fault

Marine Sediments Hydrogenous Cosmogenous Lithogenous Sediment Result from chemical reactions within seawater Cosmogenous Result from outer space Lithogenous Sediment Formed from the weathering and erosion of rocks Biogenous Sediment Created from the skeleton or shells of marine organisms Calcareous: made of calcium carbonate Siliceous: made of silica

Hot Spots Stationary plume of magma under a moving plate Creates volcanic islands in the middle of plates EX: Hawaiian Islands and the Emperor Seamount Chain