GEOL 100 Chapter 3: Plate tectonics
10 Feb 2019
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Oceans cover 71% of the earth"s surface. Seamounts: mountains on the seafloor that do not reach sea level. Abyssal plains: deep, smooth regions on the ocean floor. Mid ocean ridges: broad, symmetrical ridges that cross the ocean basins. 2-3 km higher than the average depth of the seafloor. Oceanic fracture zones: cracks and steps crossing the seafloor at right angles to the mid-ocean ridges. Continental shelves: submerged benches under shallow seawater, extending outward from the shoreline. Island arcs: curving chains of islands crossing the seafloor. Continental drift: hypothesis arguing the continents were once joined together but later drifted apart. Geologists gave the name gondwana to the hypothetical combination of the southern continents into a single large supercontinent. Distribution of fossil is consistent with continental drift. Glossopteris--seed bearing plant during the paleozoic time. Evidence glaciers covered places close to the equator now. Seafloor spreading: oceanic crust is spreading apart at underwater mountain belts, carrying continents apart.
