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Plate Tectonics. Preview. Section 1 Inside the Earth Section 2 Restless Continents Section 3 The Theory of Plate Tectonics Section 4 Deforming the Earth’s Crust. Concept Mapping. Section 1 Inside the Earth. Question of the Day.
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Plate Tectonics Preview Section 1 Inside the Earth Section 2 Restless Continents Section 3 The Theory of Plate Tectonics Section 4 Deforming the Earth’s Crust Concept Mapping
Section1 Inside the Earth Question of the Day If you journeyed to the center of the Earth, what do you think you would see along the way? Draw an illustration of the journey for your QOD.
Section1 Inside the Earth Objectives • Identifythe layers of the Earth by their chemical composition. • Identify the layers of the Earth by their physical properties. • Describe a tectonic plate. • Explain how scientists know about the structure of Earth’s interior.
Section1 Inside the Earth The Composition of the Earth • The Earth is divided into three layers. • Crust • Mantle • Core • Crust - the thin and solid outermost layer of the Earth above the mantle. • Crust is 5 to 100 km thick, and is the thinnest layer of the Earth.
Section1 Inside the Earth The Composition of the Earth, continued • Two types of crust—continental (land) and oceanic (ocean). • Oceanic crust is thinner and denser than continental crust.
Section1 Inside the Earth The Composition of the Earth, continued • Mantle - the layer of rock between the Earth’s crust and core. • The mantle is much thicker than the crust, it makes up about 2/3 of Earth. • We have never dug down that deep, so scientists must draw conclusions about what the mantle is made of and other physical properties from the Earth’s surface.
Section1 Inside the Earth The Composition of the Earth, continued • Core - the central part of the Earth below the mantle. • The core makes up about one-third of Earth’s mass. • Scientists think that the Earth’s core is made mostly of iron.
Section1 Inside the Earth The Physical Structure of the Earth • The Earth is divided into five physical layers: • The lithosphere • The asthenosphere • The mesosphere • The outer core • The inner core • Each layer has its own set of physical properties.
Section1 Inside the Earth Physical Structure of the Earth, continued • Lithosphere – the solid, outer layer of the Earth that consists of the crust and the rigid upper part of the mantle. • The lithosphere is divided into pieces that are called tectonic plates.
Section1 Inside the Earth Physical Structure of the Earth, continued • Asthenosphere - the soft layer of the mantle on which the tectonic plates move. • The asthenosphere is made of solid rock that flows very slowly.
Section1 Inside the Earth Physical Structure of the Earth, continued • Mesosphere - is the strong, lower part of the mantle between the asthenosphere and the outer core. • The prefix meso- means “middle.”
Section1 Inside the Earth Physical Structure of the Earth, continued • Earth’s core is divided into two parts. • The outer coreis liquid and is right under the mantle. • The inner coreis solid iron and is the center of the Earth.
Section1 Inside the Earth Tectonic Plates • Tectonic Plate – a block of lithosphere that consists of the crust and the rigid, outermost part of the mantle. • These plates make the Earth look covered in puzzle pieces.
Section1 Inside the Earth Tectonic Plates, continued • A Giant Jigsaw Puzzle Each tectonic plate fits together with the tectonic plates that surround it. • The lithosphere is like a jigsaw puzzle. The tectonic plates are like the pieces of the puzzle.
Section1 Inside the Earth Tectonic Plates, continued • A Tectonic Plate Close-Up The following Visual Concept presentation shows the Earth’s major tectonic plates and how they fit together. • The presentation also illustrates what a tectonic plate might look like if you could lift it out of its place.
Section1 Inside the Earth Tectonic Plates, continued • Tectonic plates “float” on the asthenosphere. • The plates bump into one another when they move.
Section1 Inside the Earth Mapping the Earth’s Interior • Since we can’t dig in the Earth how do we know what is there? • Scientists measure speeds of seismic waves that travel through the Earth’s interior during earthquakes. • By using seismographs, scientists have learned that the Earth is made of different layers.
Section2 Restless Continents Question of the Day What is meant by the following statement: “The United States is moving westward.” From what you know about geology and plate tectonics explain if you believe this statement to be true or false.
Section2 Restless Continents Objectives • DescribeWegener’s hypothesis of continental drift. • Explain how sea-floor spreading provides a way for continents to move. • Describe how new oceanic lithosphere forms at mid-ocean ridges. • Explain how magnetic reversals provide evidence for sea-floor spreading.
Section2 Restless Continents Continental Drift Hypothesis • Continental drift - the hypothesis that states that continents once formed a single landmass, broke up, and drifted to their present locations.
Section2 Restless Continents The Breakup of Pangaea • It was theorized that all of the present continents were once joined in a single, huge continent he called Pangaea. • Pangaea is Greek for “all earth.” • Pangaea existed about 245 million years ago.
Section2 Restless Continents Sea-Floor Spreading • Evidence supporting continental drift hypothesis comes from sea-floor spreading. • Sea-floor spreading - the process by which new oceanic lithosphere forms as magma rises toward the surface and solidifies.
Section2 Restless Continents Sea-Floor Spreading, continued • Mid-ocean ridges are underwater mountain chains that run through Earth’s ocean basins where sea-floor spreading takes place.
Section2 Restless Continents Sea-Floor Spreading, continued • Some of the most important evidence of sea-floor spreading comes from magnetic reversals recorded in the ocean floor. • Molten rock at the mid-ocean ridge contains tiny grains of magnetic minerals that act like compasses.
Section2 Restless Continents Sea-Floor Spreading, continued • When the Earth’s magnetic field reverses, the magnetic mineral grains align in the opposite direction. The new rock records the direction of the Earth’s magnetic field.
Section3 The Theory of Plate Tectonics Question of the Day If the sea floor is spreading an average of 4 cm a year, how many years did it take New York and the west coast of Africa to reach their current locations, 6,760 km apart? Calculate your answer in your science journal.
Section3 The Theory of Plate Tectonics Objectives • Describethe three types of tectonic plate boundaries. • Describe the three forces thought to move tectonic plates. • Explain how scientists measure the rate at which tectonic plates move.
Section3 The Theory of Plate Tectonics Tectonic Plate Boundaries • As scientists’ understanding of mid-ocean ridges and magnetic reversals grew, a theory was formed to explain how tectonic plates move. • Plate tectonics is the theory that explains how large pieces of the Earth’s outermost layer, called tectonic plates, move and change shape.
Section3 The Theory of Plate Tectonics Tectonic Plate Boundaries, continued • A boundary is a place where tectonic plates touch. • All tectonic plates share boundaries with other tectonic plates. • The type of boundary depends on which direction the tectonic plates move.
Section3 The Theory of Plate Tectonics Tectonic Plate Boundaries, continued • Three types of boundaries: • Convergent Boundaries • Divergent Boundaries • Transform Boundaries
Section3 The Theory of Plate Tectonics Tectonic Plate Boundaries, continued • Convergent boundary – the boundary formed by the collision of two lithospheric plates. • What happens at convergent boundaries depends on the kind of crust at the leading edge of each tectonic plate.
Section3 The Theory of Plate Tectonics Tectonic Plate Boundaries, continued • Divergent boundary – the boundary between two tectonic plates that are moving away from each other. • New sea floor forms at divergent boundaries. Sea-Floor Spreading.
Section3 The Theory of Plate Tectonics Tectonic Plate Boundaries, continued • Transform boundary – the boundary between tectonic plates that are sliding past each other horizontally. • The San Andreas Fault in California is an example of a transform boundary.
Section3 The Theory of Plate Tectonics Causes of Plate Movement • What causes the motion of tectonic plates? • Tectonic plates move because of changes in the density in the asthenosphere. • The following Visual Concept presentation examines three possible driving forces of tectonic plate motion.
Section3 The Theory of Plate Tectonics Tracking Plate Movement • Tectonic plate movements are so slow and gradual that you can’t see or feel them. • Tectonic plate movement is measured in centimeters per year. • Scientists use a system of satellites called the global positioning system (GPS) to measure the rate of tectonic plate movement.
