1. Unit 6 Lesson 4 Plate Tectonics
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2. Unit 6 Lesson 4 Plate Tectonics
Florida Benchmarks
SC.7.N.1.5 Describe the methods used in the pursuit of a scientific explanation as seen in different fields of science such as biology, geology, and physics.
SC.7.E.6.1 Describe the layers of the solid Earth, including the lithosphere, the hot convecting mantle, and the dense metallic liquid and solid cores.
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3. Unit 6 Lesson 4 Plate Tectonics
Florida Benchmarks
SC.7.E.6.2 Identify the patterns within the rock cycle and relate them to surface events (weathering and erosion) and sub-surface events (plate tectonics and mountain building).
SC.7.E.6.5 Explore the scientific theory of plate tectonics by describing how the movement of Earth’s crustal plates causes both slow and rapid changes in Earth’s surface, including volcanic eruptions, earthquakes, and mountain building.
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4. Unit 6 Lesson 4 Plate Tectonics
Florida Benchmarks
SC.7.E.6.7 Recognize that heat flow and movement of material within Earth causes earthquakes and volcanic eruptions, and creates mountains and ocean basins.
LA The student will organize information to show understanding (e.g., representing main ideas within text through charting, mapping, paraphrasing, summarizing, or comparing/contrasting).
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5. Puzzling Evidence What evidence suggests that continents move?
Unit 6 Lesson 4 Plate Tectonics
Puzzling Evidence
What evidence suggests that continents move?
In the late 1800s, Alfred Wegener proposed his hypothesis of continental drift.
According to this hypothesis, the continents once formed a single landmass, broke up, and drifted.
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6. What evidence suggests that continents move?
Unit 6 Lesson 4 Plate Tectonics
What evidence suggests that continents move?
Several lines of evidence supported Wegener’s hypothesis.
Fossils of the same species are found on continents on separate sides of the Atlantic Ocean.
The locations of mountain ranges and rock formations and evidence of ancient climatic conditions also supported Wegner’s hypothesis.
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7. Unit 6 Lesson 4 Plate Tectonics
What is Pangaea?
Today, scientists accept that the continents were once joined.
About 245 million years ago, the continents were joined in a single large landmass called Pangaea.
Over millions of years, Pangaea broke into fragments that drifted and collided with each other.
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8. What is Pangaea? Unit 6 Lesson 4 Plate Tectonics 8
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9. What discoveries support the idea of continental drift?
Unit 6 Lesson 4 Plate Tectonics
What discoveries support the idea of continental drift?
Scientists did not accept Wegener’s ideas because they could not determine how continents moved.
In the mid-1900s, scientists began mapping the sea floor and discovered features that supported some of Wegener’s ideas.
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10. What discoveries support the idea of continental drift?
Unit 6 Lesson 4 Plate Tectonics
What discoveries support the idea of continental drift?
Scientists discovered that oceanic crust is young compared to continental crust.
They also discovered that sea floor rock contains magnetic patterns.
A process called sea-floor spreading explains the age and magnetic pattern of sea floor rocks.
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11. What discoveries support the idea of continental drift?
Unit 6 Lesson 4 Plate Tectonics
What discoveries support the idea of continental drift?
Through sea-floor spreading, molten rock rises at the ridges and forms new oceanic crust.
Older crust is pushed away from the ridge, and the sea floor slowly spreads apart.
Scientists also discovered huge trenches in the sea floor where oceanic crust sinks into the asthenosphere.
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12. A Giant Jigsaw What is the theory of plate tectonics?
Unit 6 Lesson 4 Plate Tectonics
A Giant Jigsaw
What is the theory of plate tectonics?
Scientists began to form a new theory to explain how tectonic plates move.
Plate tectonics is a theory that describes large-scale movements of Earth’s lithosphere.
It describes why and how continents move and explains how many of the features on Earth’s crust form.
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13. What is a tectonic plate?
Unit 6 Lesson 4 Plate Tectonics
What is a tectonic plate?
The lithosphere is divided into pieces called tectonic plates, which move around on top of the asthenosphere.
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14. Boundaries What are three types of plate boundaries?
Unit 6 Lesson 4 Plate Tectonics
Boundaries
What are three types of plate boundaries?
The three types of plate boundaries are convergent boundaries, divergent boundaries, and transform boundaries.
Each type is associated with characteristic landforms.
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15. What are three types of plate boundaries?
Unit 6 Lesson 4 Plate Tectonics
What are three types of plate boundaries?
Convergent boundaries form where two plates collide. This can happen in three ways, depending on the type of crust that is involved.
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16. What are three types of plate boundaries?
Unit 6 Lesson 4 Plate Tectonics
What are three types of plate boundaries?
At a divergent boundary, two plates move away from each other, and magma forms new lithosphere at mid-ocean ridges.
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17. What are three types of plate boundaries?
Unit 6 Lesson 4 Plate Tectonics
What are three types of plate boundaries?
A boundary at which two plates move past each other horizontally is called a transform boundary. At transform boundaries, the motion of the two plates often produces earthquakes.
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18. Hot Plates What causes tectonic plates to move?
Unit 6 Lesson 4 Plate Tectonics
Hot Plates
What causes tectonic plates to move?
Scientists have proposed three mechanisms to explain how tectonic plates move over Earth’s surface.
Some evidence suggests that convection, or the movement of material due to differences in density, in the mantle drags the overlying tectonic plates along with it.
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19. What causes tectonic plates to move?
Unit 6 Lesson 4 Plate Tectonics
What causes tectonic plates to move?
The mechanism called ridge push suggests that as lithosphere sinks, the plates are pushed away from the mid-ocean ridge.
The crust along the mid-ocean ridge is less dense. As it cools, it becomes denser and sinks into the mantle, pulling it away from the ridge.
The force of the asthenosphere below pushes the rest of the plate away from the mid-ocean ridge.
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20. What causes tectonic plates to move?
Unit 6 Lesson 4 Plate Tectonics
What causes tectonic plates to move?
The mechanism called slab pull suggests that plates move because sinking plates pull them.
The leading edge of a sinking plate is colder and denser than the mantle, so it sinks. The rest of the plate follows.
Many scientists think slab pull is the most important mechanism driving plate motion.
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