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Plate Tectonics. Geologic History Structure of the Earth The Rock Cycle Continental Drift Theory Theory of Plate Tectonics Plate Boundaries. Plate Tectonics - Continental Drift. Definition: Continental Drift.
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Plate Tectonics • Geologic History • Structure of the Earth • The Rock Cycle • Continental Drift Theory • Theory of Plate Tectonics • Plate Boundaries
Definition: Continental Drift • It is the theory that the earth’s continents are constantly in motion and at one time they all collided together to form one massive continent about 300 million years ago!
Founder of the Continental Drift Theory • Alfred Wegener came up with the idea in the early 1900’s. • He believed that the world shared certain characteristics that proved that at one time the continents were all together.
Proof # 1 • Visually, he saw that the continents of Africa and South America would fit together.
Proof # 2 • There were fossils of animals and plants on both continents!
Proof # 3 • There are mountain ranges and structures on different continents that could be lined up if they were one large continent. • For example: Appalachian and Caledonian Mountains
Proof # 4 • There is proof that ice sheets had once covered the southern portions of South America, Australia, India and Africa. Glaciers could have only formed if the continents were together. • However, theory was debated because scientists wanted evidence to explain movement of continents.
Plate Tectonics & Convection Currents • Theory of Plate Tectonics offered a more scientifically sound explanation for the movement of continents. • Plate Tectonics is the movement of the earth’s surface which is divided into 6 major plates. Within each major plate, there are numerous sub-plates as well. • Large convection currents in the mantle cause plates to move (hot liquid rises toward earth’s surface – moves along earth’s surface – cools and comes back down toward mantle – causes mantle rock to shift) • Plate boundariesoccur when 2 or more plates meet each other
1. Divergent • Found in the middle of the Atlantic Ocean (mid-Atlantic Ridge) New land is created by volcanic activity.
2. Convergent • Found in the Himalayas. Fold mountains and trenches are created.
3. Subduction • Takes place at convergent boundaries • One plate moves underneath the other plate • Found on Canada’s West Coast. Volcanoes are produced along with earthquakes at great depths.
3. Subduction - Volcanoes • The plate moving deeper into the earth melts due to the hot temperature, melting the earth’s crust into liquid form called molten. • The molten finds a hole in the ground and builds up creating a volcano. Molten inside the volcano is called magma. When the volcano explodes due to gas build up (hot temperatures), magma becomes lava. Lava cools and turns into rock on the earth’s surface.
Ring of Fire • ↑ of tectonic plate activity • 75% world’s active volcanoes • 90% world’s earthquakes; 80% world’s largest earthquakes
4. Transform • Found in California (San Andreas Fault). • Earthquakes are produced.
4. Transform - Earthquakes • Less than 3.5 Generally not felt, but recorded. • 3.5-5.4 Often felt, but rarely causes damage. • Under 6.0 At most slight damage to well-designed buildings. • 6.1-6.9 Can be destructive in areas up to about 100 kilometers across. • 7.0-7.9 Major earthquake. Can cause serious damage over larger areas. • 8 or greater Great earthquake. Can cause serious damage in areas several hundred kilometers across.
Geologic History • Precambrian Era Vulcanism Fault Ancient Sea Igneous Rock
Geologic History • Paleozoic Era Erosion Erosion Sediments Sediments Igneous Rock
Geologic History • Mesozoic Era Erosion Sediments Sediments Igneous Rock Mountains Forming
Geologic History • Cenozoic Era Sedimentary Mountains Eroding Mountains Forming Sedimentary Plains APPALACHIAN MOUNTAINS PACIFIC OCEAN ROCKY MOUNTAINS Igneous Rock ATLANTIC OCEAN INTERIOR PLAINS CANADIAN SHIELD
Earth’s Interior HYDROSPHERE ATMOSPHERE Air Water Crust - 8-64 km thick - cold & fragile - Granite and Basalt Land LITHOSPHERE Mantle - 1800 km thick - hot & molten - Magnesium and Silicon Outer Core - 2000 km thick - 3 - 4000°C - liquid Nickel and Iron Inner Core - 1400 km thick - 5 - 6000°C - solid Nickel and Iron
Types of Rocks Igneous rocks are recognized by: • often has crystals oriented randomly • the presence of vesicules (holes) in extrusive igneous rocks • may be dark-colored and heavy • may display two grain sizes, one much larger than the other • the slower the cooling, the larger the crystals • e.g., Basalt, Granite, Pumice
Types of Rocks Sedimentary rocks are recognized by: • grains cemented together • the presence of fossils • light-colored and light weight • may display visible layers • e.g., Sandstone, Limestone, Coal, Shale
Types of Rocks Metamorphic rocks are recognized by: • banded light and dark colors • "ching" sound instead of a "chunk" sound when tapped • e.g., Quartzite, Marble, Slate
Rock Cycle MAGMA Heats and melts Cools and hardens IGNEOUS METAMORPHIC Weathers, erodes, and deposits Stresses or heats SEDIMENTARY
