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Transcript
Outer Core Liquid layer of Earth’s core Surrounds inner core Lithosphere Outermost layer of Earth Made of crust and upper mantle Divided into pieces called tectonic plates. The crust is divided into continental plates which drift slowly (only a few centimeters each year) atop the less rigid mantle. The crust is thinner under the oceans (6-11 km thick); this is where new crust is formed. Continental crust is about 25-90 km thick. The lithosphere is defined as the crust and the upper mantle, a rigid layer about 100-200 km thick. The Mohorovicic discontinuity is the separation between the crust and the upper mantle. Continental Drift Scientist Alfred Wegener had a theory called continental drift. A hypothesis that states that the continents once formed a single land mass, over a LONG PERIOD OF TIME broke apart and eventually drifted to their present location. This land mass was called Pangaea. Wegener’s Theory Wegener’s hypothesis seemed to explain several things: Puzzle Theory: How well the continents fit together, like a puzzle. Fossil Pattern: Fossils of the same plant and animal species are found on continents that are on different side of the Atlantic. Rocks: Rock formations and rock dating showed that these rocks and formations were the same age, thus leading scientists to believe that they were once connected into similar rock formations, such as mountain chains. Fossil Evidence The Rocks Match Broad belts of rocks in Africa and South America are the same type. Broad rock belts in North America, the British Isles and Scandinavia match. These broad belts then match when the end of the continents are joined. Mid-Ocean Ridge & Sea-Floor Spreading A chain of submerged mountain ranges that runs through the center of the Atlantic Ocean. Sea-floor spreading takes place along the mid-ocean ridge Sea- Floor Spreading Sea-floor spreading is the process by which new oceanic lithosphere forms as magma rises toward the surface and solidifies or hardens. As tectonic plates move away from one another, the sea floor spreads apart and magma fills in the gaps, creating new ocean floor. The Theory of Plate Tectonics The Earth’s lithosphere (crust and upper mantle) is divided into tectonic plates. This includes oceanic crust, too. These plates move on top of the asthenosphere (lower mantle). We know that these plates move in different ways. Tectonic Plate Boundaries A boundary is a place where tectonic plates touch. There are 3 types of tectonic plate boundaries: Convergent Divergent Transform Convergent Boundary When two plates collide, or move toward each other, the boundary is called convergent There are 3 types of convergent boundaries, depending on what type of crust comes together. Continental-continental Continental-oceanic Oceanic-oceanic Convergent Boundary Continental-Continental The two continental plates come together Buckle Thicken Push continental crust upward Convergent Boundary Continental-Oceanic Dense oceanic crust sinks below the continental crust and sinks into the asthenosphere. This is a subduction zone. Sub means below (submarine, subway) Old ocean crust is pushed below the asthenosphere and gets re-melted and recycled. Convergent Boundary Oceanic-Oceanic One oceanic plate sinks below the other. Another subduction zone Divergent Boundary Two tectonic plates move away from each other. On the sea floor at the mid ocean ridge this is called sea floor spreading. As the plates move apart, magma rises to fill the gaps. The magma is cooled and forms new ocean floor. The volcanic country of Iceland, which straddles the Mid-Atlantic Ridge, offers scientists a natural laboratory for studying on land the processes also occurring along the submerged parts of a spreading ridge. Iceland is splitting along the spreading center between the North American and Eurasian Plates, as North America moves westward relative to Eurasia. Transform Boundary Two tectonic plates move past one another. Their edges are jagged and irregular. As they grind together and jerk, they slide past each other creating earthquakes. Tectonic Plate Theory The theory of plate tectonics was developed in the 1960's. This theory explains the movement of the Earth's plates (which has since been documented scientifically) and also explains the cause of earthquakes, volcanoes, oceanic trenches, mountain range formation, and many other geologic phenomenon. The plates are moving at a speed that has been estimated at 1 to 10 cm per year. Most of the Earth's seismic activity (volcanoes and earthquakes) occurs at the plate boundaries. What happens at these plate boundaries? Sea-Floor Spreading- new ocean floor created Volcanoes Earthquakes Mountain building TYPES OF PLATE MOVEMENT: Divergent, Convergent and Transform Boundaries Divergent Boundary- Plates move away from each other Convergent Boundary-Plates move toward each other Transform Boundary- Plates move past each other Convergent Boundary When two plates collide (at a convergent plate boundary), some crust is destroyed in the impact and the plates become smaller. The results differ, depending upon what types of plates are involved. 1.Oceanic Plate and Continental Plate When a thin, dense oceanic plate collides with a relatively light, thick continental plate, the oceanic plate is forced under the continental plate; this phenomenon is called subduction zone. 2. Two Oceanic Plates - When two oceanic plates collide, one may be pushed under the other and magma from the mantle rises, forming volcanoes in the vicinity. 3. Two Continental Plates - When two continental plates collide, mountain ranges are created as the colliding crust is compressed and pushed upwards. Oceanic Oceanic Volcanoes will usually form in the area. Continental Continental Mountains are formed. Transform Boundary Two tectonic plates move past one another. Their edges are jagged and irregular. As they grind together and jerk, they slide past each other creating earthquakes. QUIZ 1. Boundary where two plates move away from each other_____________ 2. Boundary where two plates move toward each other_________________ 3. Boundary where two plates move past each other ________________ 4. When two oceanic plates move away from each other it is called_______. 5. When an oceanic plate moves below a continental plate a_____zone is created. 6. The underwater chain of mountains in the Atlantic ocean caused by a divergent boundary is _____. 7. Theory that states that all of the continents were one large land mass millions of years ago is__________. 8. The theory that explains the movement of tectonic plates is_______. 9. The giant land mass that Wegener says existed millions of years ago is called________. 10. Made of crust and upper mantle_________. 11. Is made up of tectonic plates_________. 12. Consists of mantle, tectonic plates move on top of this_________. 13. A current of heat flows from the core to the crust. This movement of magma causes plates to move. _____________. 14. Outermost layer of the Earth_________. 15. Contains most of Earth’s mass___________. 16. Center of the Earth that is made mostly of iron and nickel___________. QUIZ 1. Boundary where two plates move away from each other__divergent boundary 2. Boundary where two plates move toward each other__convergent boundary 3. Boundary where two plates move past each other __transform boundary 4. When two oceanic plates move away from each other it is called_sea floor spreading 5. When an oceanic plate moves below a continental plate a_seduction zone is created. 6. The underwater chain of mountains in the Atlantic ocean caused by a divergent boundary is _a midocean ridge. 7. Theory that states that all of the continents were one large land mass millions of years ago is_the tectonic plate theory 8. The theory that explains the movement of tectonic plates is_plate tectonics 9. The giant land mass that Wegener says existed millions of years ago is called__pangea 10. Made of crust and upper mantle__lithosphere 11. Is made up of tectonic plates__the earth’s surface 12. Consists of mantle, tectonic plates move on top of this__aesthenosphere 13. A current of heat flows from the core to the crust. This movement of magma causes plates to move. _____________. 14. Outermost layer of the Earth__lithosphere. 15. Contains most of Earth’s mass___________. 16. Center of the Earth that is made mostly of iron and nickel___________.
