* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download File
Survey
Document related concepts
Ocean acidification wikipedia , lookup
Schiehallion experiment wikipedia , lookup
Anoxic event wikipedia , lookup
Paleontology wikipedia , lookup
Geochemistry wikipedia , lookup
Age of the Earth wikipedia , lookup
Physical oceanography wikipedia , lookup
Geomagnetic reversal wikipedia , lookup
Oceanic trench wikipedia , lookup
History of geomagnetism wikipedia , lookup
History of Earth wikipedia , lookup
Abyssal plain wikipedia , lookup
History of geology wikipedia , lookup
Supercontinent wikipedia , lookup
Large igneous province wikipedia , lookup
Transcript
Plate Tectonics • Ever notice how all the continents appear to fit together like a jigsaw puzzle? • Scientists often wondered why opposing coastlines had similar geographic features. Plate Tectonics • The study of how the Earth’s crust moves. – The surface of the Earth is made up of a number of plates that have moved over millions of years. Continental Drift • In 1915, the “puzzle pieces” led German scientist, Alfred Wegner, to purpose the theory of continental drift. • His theory explains that the continents were once pieced together forming the supercontinent called Pangea. – Believes all continents are presently moving on the Earth’s surface. Pangea • Wegner believed the continents were joined together 225 million years ago to form the supercontinent called Pangea. – Pangea means "ALL LAND” • About 200 million years ago, Pangea began to break apart forming the current position of the continents. Evidence of Pangea and Continental Drift 1. Matching Mountain Ranges – Mountain ranges on the east coast of North America and west coast of Europe and Africa are similar in size and composition. • They are made of the same rocks and minerals! Evidence of Pangea and Continental Drift 2. Fossil Clues – Plants and animal fossils were found at similar locations where continents were thought to have been connected. (Ex. Lystrosaurus, Mesosaurus) Evidence of Pangea and Continental Drift • Mesosaurus Fossils – A freshwater reptile, found in South America and Africa. – The same fossils, separated by an ocean. How can this happen? The Plates must have been joined together in the past. Evidence of Pangea and Continental Drift • • Fossil Clues: Glossopteris Fossil – Tropical plant found in Antarctica!! How did it get there? The plates must have been joined together in the past . Evidence of Pangea and Continental Drift 3. Climate clues: – Glaciers: By viewing rock samples in southern Africa, India, South America, and Antarctica, observations indicate striations in the bedrock. • Striations are grooves in the rock that indicate glacial movement. •How can the same striations be on different sides of the world? •The continents must have been joined together in the past! Striations Evidence of Pangea and Continental Drift Climate clues: Glaciers • Glaciers once covered southern areas of Africa, India, and South America. – As glaciers move, they carve grooves in the bedrock. Evidence of Pangea and Continental Drift • Present day of the continents. Notice the locations of where the glaciers once were. How did it get there?? Even though Wegner had some compelling evidence about continental drift, the scientific community never did accept his theory! Why not???? Wegner could never prove how the continents moved. Do Now 1. According to Wegener's hypothesis that continents are moving today, what supercontinent apparently broke up about 200 million years ago? a) Eurasia b) Mesopotamia c) Pangea d) Caucasia 2. Besides the fitting together of the continents, Wegener’s idea of continental drift was based upon which of the following? a) Mid-ocean-ridge system c) Color of the sand in N. America b) Fossils found in S. America and Africa d) Gravitational pull of the moon 3. Although Wegener presented an interesting theory of continental drift. What was the one part of his continental drift theory that he could not convince others was possible?? a)“Land bridges” were proven to have connected S. America and Africa that aided migration of species found as fossils. b) The mountain ranges on both sides of the Atlantic ocean are similar in composition c) The way that continents move through solid ocean floors d) The locations of tropical plants on Antarctica. Do Now Do Now • Explain why Wegner’s Hypothesis of continental drift was not accepted by the scientific community. • Come up with your own hypothesis of why the continent drifted apart Evidence of Crustal Movement 1. Seafloor spreading – Mid Atlantic Ridge – Convection currents – Magnetic Reversal 2. Hawaiian Hotspots Evidence of Crustal Movement 1. Seafloor spreading • Henry Hess, a U.S. geologist supported Wegner’s theory of continental drift. – Stated that ridges in the middle of the oceans are pulling apart causing magma to rise to the surface creating new ocean floor at mid ocean ridges. Evidence of Crustal Movement 1. Seafloor spreading: • As magma rises, old rock gets pushed to the sides as new rock forms in the middle of the ridge. – Oldest rocks in the ocean are only 180 million years old Mid ocean Ridge New rock Old rock Old rock Convection Currents cause movement 1. Seafloor Spreading: •Convection – Process by which materials with high heat rise, then cool and sink, and re-circulate. •What causes hot material to rise and cool material to sink? DENSITY!! Convection Cell Animation Evidence of Crustal Movement 1. Seafloor Spreading: Magnetic Reversal: • Some rocks contain magnetite: – mineral that has a magnetic field. • As magma rises, cools, and hardens, the magnetic material will point in the direction of Earth’s magnetic field. Evidence of Crustal Movement Magnetic Reversal: • Rock records show that Earth’s magnetic field has reversed repeatedly throughout history. – Alternating bands of rock pointing North and South along mid ocean ridges. Do Now Hawaii is a chain of islands that rests in the middle of the Pacific plate, not near any plate boundary. Attempt to explain Hawaii’s volcanic activity in 3-4 sentences. Evidence of Crustal Movement 2. Hawaiian Hotspots: • Hotspots are areas in the ocean where magma breaks through the surface creating an island. As the plate continues to move over the hotspot, new islands begin to “pop up”. Do Now • Describe the process of seafloor spreading. • What is the driving force behind seafloor spreading? • How does the record of earth’s magnetic field support the theory of seafloor spreading? • What is a Hot Spot? Earth’s Interior • By studying and interpreting earthquake data and seismic waves, scientists believe they can map the different layers of the Earth. Layers of the Earth • Crust - Thin outer most layer of the Earth, including the ocean floor – relatively low density and brittle. • Most earthquakes occur within the crust. Layers of the Earth • Lithosphere: Made up of the crust and upper part of the mantle (approx. 100km thick). – Tectonic plates make up the lithosphere. Layers of the Earth • Mantle: Approx. 2,000 miles thick, directly below the crust. • Upper part of the mantle is called the Asthenosphere •Acts like a liquid •The lithosphere floats on top Layers of the Earth • Outer “ Liquid” Core – Believed to behave as a thick liquid composed of liquid iron. Layers of the Earth • Inner “ Solid” Core: consists of iron and nickel. – Scientists believe that samples of meteorites containing iron and nickel can infer the composition of the Earths core. Do Now 1. List in order (outside – in) the layers of the Earth. *include Asthenosphere and Lithosphere. 2. Which layer is believed to be composed of liquid Iron? 3. Which layers contains the tectonic plates? Plate Tectonics Earth’s crust is broken up into 2 types of plates: 1. Continental “Land” Plates – Thicker than oceanic plates. Density = 2.7g/cm³ 2. Oceanic “ocean” Plates – Thinner and more dense than continental plates. Density = 3.0g/cm³ Type of Crust Average Thickness Average Age Major Component Continental Crust 20-80 kilometers 3 billion years Granite Oceanic Crust 10 kilometers Generally 70 to 100 million years old Basalt Plate Boundaries Plate boundaries – The place where 2 plates meet. S. Amer Nazca 3 types of boundaries 1. Divergent boundary 2. Convergent boundary 3. Transform boundary Divergent “Divide” Boundaries • Where 2 plates move apart from each other. – Tensional forces pull apart Features 1. Rift valley 2. Mid ocean ridge Divergent “Divide” Boundaries Mid Ocean Ridge Do now 1. What types of convergent boundaries will create volcanic activity? 2. Which type of boundary is know as the “mountain builder”? 3. What occurs at a subduction zone? Convergent “come together” Boundaries • Where 2 plates collide into each other. – When 2 plates collide, the denser plate gets pushed under the less dense plate. 3 plate combinations are possible: 1. Oceanic– Continental 2. Oceanic – Oceanic 3. Continental– Continental 1. Oceanic – Continental • More dense ocean plate is pushed under the less dense continental plate. – Area where ocean plate is pushed into the mantle is called the SUBDUCTION ZONE. Features • Trenches • Volcanic ranges 1. Oceanic – Continental • Andes Mountains – South America • Deep sea trench • Volcanic Mountain Range 2. Oceanic – Oceanic •2 ocean plates collide. •The cooler, more dense plate gets subducted. Features: •Trench •Island arc volcanoes 2. Oceanic – Oceanic • Alaska – The Aleutian Islands are an Island arc created by 2 ocean plates colliding. 3. Continental– Continental •2 continental plates collide. •NO SUBDUCTION. Both plates are less dense than ocean plates. Features: •“Mountain Builders” 3. Continental– Continental •Himalayas – Mountain range that borders North India and Southern Tibet. •Highest peaks in the world! •Everest = 29,035 ft •K2 = 28,250 ft •Hunter Mtn. N.Y. = 4,000ft Transform Boundary •2 plates slide past each other in opposite directions, or the same direction but different rates. Features: •Hotspot for earthquakes •San Andreas Fault Transform Boundary •San Andreas fault in California. Do Now • Using you plate tectonics map, place an X on the following coordinates • 10 N, 80 E • 50 S, 120 W • 45 N, 80 W • 65 S, 60 W • 40 N, 140 E