Plate Tectonics.pdf

Plate Tectonics This PhotoThis Photo by Unknown Author is licensed under CC BY-SA Plate Tectonics Continental Drift Plate Tectonics Continental Drift 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...

Plate Tectonics This PhotoThis Photo by Unknown Author is licensed under CC BY-SA Plate Tectonics Continental Drift Plate Tectonics Continental Drift 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! ●Pangaea (meaning “all lands”) began to break up and drift apart. This PhotoThis Photo by Unknown Author is licensed under CC BY-SA 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. ●He had 4 pieces of proof. Proof # 1 Proof #1 Visually, he saw that the continents of Africa and South America would fit together like a jigsaw puzzle. Proof #2 There were fossils of plants and animals on more than one continent ● There were fossils of animals and plants on both continents! Proof # 3 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 Proof #4 ● There is proof that ice sheets had once covered the southern portions of South America, Australia, India and Africa – how could this happen in places that are so warm today? Glaciers could have only formed if the continents were close to the south pole. How????? ●However, the theory was debated because scientists wanted evidence to explain how the continents could drift across the earth’s surface. •Theory of Plate Tectonics offered a more scientifically sound explanation for the movement of continents. …thus the theory of PLATE TECTONICS (1960s) •Plate Tectonics is the movement of the earth’s surface (crust) which is divided into 6 major plates. Within each major plate, there are numerous sub-plates as well. This PhotoThis Photo by Unknown Author is licensed under CC BY-SA •Large convection currents in the mantle cause plates to move. •The mantle lies under the crust. •Earth radiates huge amounts of energy from the radioactive decay of elements in the core. Plate Tectonics Continued… This energy makes its way outwards through the mantle toward the crust •This heat gives the mantle “plastic” characteristics, which means that it is very slowly moving with giant convection cells that carry the heat to the Earth’s surface. Convection Currents: 4 types of Boundaries •Plate boundaries occur when 2 or more plates meet each other. There are 4 types of plate boundaries. •1) Divergent •2) Convergent •3) Subduction •4) Transform Plate Tectonics Map ●Formed when 2 plates move away from each other ●Found in the middle of the Atlantic Ocean (mid-Atlantic Ridge) . 1. Divergent This PhotoThis Photo by Unknown Author is licensed under CC BY-SA ●New land is created by volcanic activity. The Mid-Atlantic Ridge is a divergent boundary. Sea floor spreading: ●Created when 2 plates move towards each other ●Found in the Himalayas. 2. Convergent ●Fold mountains and trenches are created. This PhotoThis Photo by Unknown Author is licensed under CC BY-SA 2. Convergent ● 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 This PhotoThis Photo by Unknown Author is licensed under CC BY-SA ● The plate moving deeper into the earth melts due to the hot temperature, melting the earth’s crust into liquid form called molten. 3. Subduction - Volcanoes ● 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. This PhotoThis Photo by Unknown Author is licensed under CC BY-SA 3. Subduction - Volcanoes ●Occur when 2 plates slide past each other ●Found in California (San Andreas Fault). 4. Transform ●Earthquakes are produced. Transform Boundary 4. Transform 4. Transform Tectonic setting of western British Columbia and Washington state. The oceanic Juan de Fuca plate is moving beneath the continental North America plate at a rate of about 4 cm/year. Great earthquakes occur along part of the boundary between the two plates. Divergent Convergent Subduction Transform Moveme 2 plates nt move away from each other 2 plates move towards each other One plate 2 plates moves under slide past the other each other Summary What is formed New Land Fold Mountains or Rift Valley Example Mid Atlantic Himalayas. Ridge Volcanoes Earthquakes and Earthquakes West coast San Andreas of Canada Fault in California Pacific Ring of Fire Plate Tectonics video (21:49) Learn 360 Increase in tectonic plate activity 75% World’s active volcanoes 90% World’s earthquakes Plate Tectonics - Our Restless Earth - YouTube Vi ●