PLATE TECTONICS
1950’s scientists first knew earth’s plates were moving. Alfred Wegener proposed in 1915 Fossils on different continents match.
Continental Drift 1620 - Sir Francis Bacon maps Atlantic Ocean and notices parallelism of opposite shores 1915 - Alfred Wegener proposes Pangea breaks apart & ocean fills gaps. Based on fossil evidence, rock types and rock structures Magnetic Studies - Outer core generates magnetic field (polarity of North & South Poles). Patterns of polarity reversals in mid-ocean ridge and volcanic rocks where magma reaches surface. magnetic field & seafloor spreading
New ocean crust is being created, pushing continents apart. Youngest rock Oldest rock Mid Atlantic Ridge New ocean crust is being created, pushing continents apart.
Earthquakes occur along moving plate boundaries. Mid Atlantic Ridge Ring of Fire Earthquakes occur along moving plate boundaries. Four plates
Oceanic plates generally made of basalt (more dense & darker) Continental plates (crust) generally made of granite. Less dense than oceanic plates Oceanic plates generally made of basalt (more dense & darker) When these two plates meet, oceanic plate is forced under the continental plate.
What happens at each type of boundary? PLATE BOUNDARIES 2 continental plates = Himalayas 2 continental plates = Rift Valley 2 oceanic plates = Islands 2 oceanic plates = sea floor spreading (ridge) 2 plates = earthquakes Practice
Plate visual http://www.iris.edu/hq/files/programs/ed ucation_and_outreach/aotm/interactive/ DynamicPlanet-EQs&Volcanoes.swf
Movement of plates is driven by convection currents. Hot interior of earth rises, cools and sinks.
Examples: Hawaii, Yellowstone, Galapagos, Iceland, others. HOT SPOTS - places where magma is close to surface, but not necessarily at a plate boundary Examples: Hawaii, Yellowstone, Galapagos, Iceland, others.
VOCABULARY Plate tectonics transform boundary convergent boundary divergent boundary rift ridge seafloor spreading magnetic reversal hot spot convection