260 likes | 516 Views
Internal forces shaping the earth ch. 4.1. Earth’s Layers:. Core – Inner: solid metallic center of Earth Outer: liquid metallic center of Earth Mantle – soft layer of molten rock (Magma) floating on the core Crust – thin layer of rock at the surface. Volcanoes –
E N D
Earth’s Layers: • Core – • Inner: solid metallic center of Earth • Outer: liquid metallic center of Earth • Mantle – • soft layer of molten rock (Magma) floating on the core • Crust – • thin layer of rock at the surface
Volcanoes – • Openings in Earth's crust thru which molten lava, ash, &gases are ejected • Magma – • Molten rock beneath the surface • Lava – • Molten rock on the surface
1912: Alfred Wegener: • Suggested Continental Drift Theory after looking at map of world • Found fossils of extinct animals on different continents
1950s & 1960s: ocean floor was studied • Underwater mtns. ring the edges of continents • 1968: • dfdf
1968: Theory of Plate Tectonics • Earth’s crust is divided into rigid plates that move slowly on the upper mantle—set in motion by convectional heat from the core • Move in different directions • Over 12 plates
Pangaea • When all of Earth’s continents were one (225 mill. yrs. Ago)
Laurasia • Northern half of Pangaea • Gondwanaland • Southern half of Pangaea
Plate Boundaries • Divergence: • Spreading/pulling apart • Mid-Atlantic Ridge • Iceland / Surtsey • Video clip
Convergence: • Continental plates crash into one another • Himalaya Mtns.
Subduction: • Lesser oceanic plate is forced under dominant continental plate • Trenches (Mariana Trench) • Mountains (Japan, Andes Mtns., Cascade Mtns.) • Video clip
Transform: • Plates move laterally passed one another • New Madrid, MO • San Andreas Fault
SOME Geologically-Active Places: • Ring of Fire: • Geologically-active region around the perimeter of the Pacific Ocean • 75% (452) of world’s active & dormant volcanoes • 90% of world’s earthquakes • Video clip
Great Rift Valley: • Divergent plate boundary in E. Africa
Mariana Trench: • Subduction plate boundary • Deepest part of the ocean • Challenger Deep • >36,000 ft. deep • James Cameron (March 2012) • ddf