CHAPTER 4: PLATE TECTONICS LESSON 1: CONTINENTAL DRIFT QUIZ G 1.Wegener proposed the continental drift hypothesis suggesting that continents are in constant

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  • Slide 1
  • CHAPTER 4: PLATE TECTONICS LESSON 1: CONTINENTAL DRIFT QUIZ G 1.Wegener proposed the continental drift hypothesis suggesting that continents are in constant motion on the surface of the Earth. 2.Glossopteris was a supercontinent consisting of Earths present-day continents. 3.One of Alfred Wegeners pieces of evidence for continental drift was data from the seafloor. 4.Wegener used fossils to suggest that a supercontinent existed about 250 million years ago.
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  • CHAPTER 4: PLATE TECTONICS LESSON 1: CONTINENTAL DRIFT QUIZ G 5.Glacial grooves in rocks in Africa suggest that this continent was once located in a much colder place. 6.Rocks with a similar makeup and age in South America and Africa supported Wegeners idea of moving continents. 7.Wegeners hypothesis of moving continents was accepted by many because he had lots of data to support it. 8.The puzzlelike fit of continental coastlines was one piece of evidence Wegener used to suggest that the continents were once joined.
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  • CHAPTER 4: PLATE TECTONICS LESSON 1: CONTINENTAL DRIFT QUIZ A 1. 1.State Alfred Wegeners hypothesis of continental drift. 2. 2.Explain how Wegener used the shapes of continents to support his hypothesis of continental drift. 3. 3.Explain how Glossopteris fossils provide evidence of continental drift. 4. 4.Identify two types of climate data used by Wegener to support his hypothesis. 5. 5.Explain how Wegener used his studies of rocks to support continental drift. 6. 6.Explain why Wegeners hypothesis was not widely accepted by scientists at the time.
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  • CHAPTER 4: PLATE TECTONICS LESSON 2: DEVELOPMENT OF A THEORY Lesson 2 Vocabulary Words: Mid-Ocean Ridge Seafloor Spreading Normal Polarity Magnetic Reversal Reversed Polarity
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  • LESSON 2: DEVELOPMENT OF A THEORY MAPPING THE OCEAN FLOOR Using an echo sounder, scientists were able to determine the depth of the ocean and create a topographic map of it in the 1940s. Using an echo sounder, scientists were able to determine the depth of the ocean and create a topographic map of it in the 1940s. These maps revealed vast mountain ranges that stretched for miles on the ocean floor. These maps revealed vast mountain ranges that stretched for miles on the ocean floor. Mid-ocean ridges are mountain ranges in the middle of the oceans, and are much longer than mountains on land. Mid-ocean ridges are mountain ranges in the middle of the oceans, and are much longer than mountains on land.
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  • LESSON 2: DEVELOPMENT OF A THEORY SEAFLOOR SPREADING By the 1960s, scientists discovered a new process that helped explain continental drift. By the 1960s, scientists discovered a new process that helped explain continental drift. Seafloor spreading is the process by which new oceanic crust forms along a mid-ocean ridge and older oceanic crust moves away from the ridge. Seafloor spreading is the process by which new oceanic crust forms along a mid-ocean ridge and older oceanic crust moves away from the ridge. When the seafloor spreads, the mantle below melts and forms magma. When the seafloor spreads, the mantle below melts and forms magma. Magma erupts on Earths surface as lava, and crystallizes on the seafloor, forming Basalt. Magma erupts on Earths surface as lava, and crystallizes on the seafloor, forming Basalt.
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  • LESSON 2: DEVELOPMENT OF A THEORY SEAFLOOR SPREADING Because the lava erupts under water, it cools rapidly and forms rounded structures called pillow lava. As the seafloor continues to spread, the older oceanic crust moves away from the mid-ocean ridge.
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  • LESSON 2: DEVELOPMENT OF A THEORY SEAFLOOR SPREADING The rugged mountains that make-up mid- ocean ridges form in two different ways: The rugged mountains that make-up mid- ocean ridges form in two different ways: 1. Large amounts of lava can erupt from the center of the ridge, cool, and build-up around the ridge. 2. As the lava cools and forms new crust, it cracks and the rocks move up or down these cracks in the seafloor, forming jagged mountain ranges.
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  • LESSON 2: DEVELOPMENT OF A THEORY SEAFLOOR SPREADING Over time, sediment accumulates in the ocean basins. Close to the mid-ocean ridge there is almost no sediment. Far from the mid-ocean ridge, the layer of sediment becomes thick enough to make the seafloor smooth. Over time, sediment accumulates in the ocean basins. Close to the mid-ocean ridge there is almost no sediment. Far from the mid-ocean ridge, the layer of sediment becomes thick enough to make the seafloor smooth. The smooth part of the seafloor is called the abyssal plain. The smooth part of the seafloor is called the abyssal plain. Continents move as the seafloor spreads along a mid-ocean ridge. Continents move as the seafloor spreads along a mid-ocean ridge.
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  • LESSON 2: DEVELOPMENT OF A THEORY DEVELOPMENT OF A THEORY The first evidence used to support seafloor spreading was discovered by studying the magnetic signature of the rocks on the seafloor. The first evidence used to support seafloor spreading was discovered by studying the magnetic signature of the rocks on the seafloor. Normal polarity is a state in which magnetized objects, such as compass needles, will orient themselves to point north. (Earth today) Normal polarity is a state in which magnetized objects, such as compass needles, will orient themselves to point north. (Earth today) Sometimes a magnetic reversal occurs, and the magnetic field reverses directions. Sometimes a magnetic reversal occurs, and the magnetic field reverses directions.
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  • LESSON 2: DEVELOPMENT OF A THEORY DEVELOPMENT OF A THEORY The opposite of normal polarity is reversed polarity- a state in which magnetized objects would reverse themselves and orient themselves to point south. The opposite of normal polarity is reversed polarity- a state in which magnetized objects would reverse themselves and orient themselves to point south. Magnetic reversals occur naturally every few hundred thousand to few million years. Magnetic reversals occur naturally every few hundred thousand to few million years.
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  • LESSON 2: DEVELOPMENT OF A THEORY DEVELOPMENT OF A THEORY Basalt on the seafloor contains iron-rich minerals that are magnetic. Basalt on the seafloor contains iron-rich minerals that are magnetic. When magnetic minerals in cooling lava crystallize, they record the direction of Earths magnetic field at the time. When magnetic minerals in cooling lava crystallize, they record the direction of Earths magnetic field at the time.
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  • LESSON 2: DEVELOPMENT OF A THEORY DEVELOPMENT OF A THEORY Scientists studied magnetic minerals in rocks from the seafloor using a magnetometer to measure and record the magnetic signature of the rocks. Scientists studied magnetic minerals in rocks from the seafloor using a magnetometer to measure and record the magnetic signature of the rocks. They discovered parallel magnetic stripes on either side of the mid-ocean ridge. They discovered parallel magnetic stripes on either side of the mid-ocean ridge. Each pair of stripes had a similar composition, age, and magnetic character. Each pair of stripes had a similar composition, age, and magnetic character. The pairs of magnetic stripes confirm that the ocean crust formed at mid-ocean ridges is carried away from the center of the ridges in opposite directions. The pairs of magnetic stripes confirm that the ocean crust formed at mid-ocean ridges is carried away from the center of the ridges in opposite directions.
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  • LESSON 2: DEVELOPMENT OF A THEORY DEVELOPMENT OF A THEORY Other measurements made on the seafloor also confirm seafloor spreading. Other measurements made on the seafloor also confirm seafloor spreading. Measurements have confirmed that more thermal energy leaves Earth near mid-ocean ridges than is released from beneath abyssal plains. Measurements have confirmed that more thermal energy leaves Earth near mid-ocean ridges than is released from beneath abyssal plains. Sediment collected from the seafloor can be dated to show that the sediment closest to the mid-ocean ridge is younger than the sediment farther away from the ridge. Sediment collected from the seafloor can be dated to show that the sediment closest to the mid-ocean ridge is younger than the sediment farther away from the ridge.
  • Slide 21
  • USING PG. 122, LABEL THE DIAGRAM IN YOUR NOTES.
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  • LESSON 2: DEVELOPMENT OF A THEORY MINI-LAB WARM-UP 15 MINUTES Using the materials on your desk, start on number 4 on the worksheet with your group. Make sure to complete number 5 and 6 in your notebook for todays warm- up.
  • Slide 23
  • LESSON 2: DEVELOPMENT OF A THEORY LESSON REVIEW Complete the lesson 2 review on page 126 in your notebook.