Name: ______________________
17.1 Objectives:
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Identify the lines of evidence that led Wegener to suggest that Earth’s continents have moved
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Discuss how evidence of ancient climates supported continental drift
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Explain why continental drift was not accepted when it was first proposed
17.2 Objectives:
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Summarize the evidence that led to the discovery of seafloor spreading
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Explain the significance of magnetic patterns on the seafloor
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Explain the process of seafloor spreading
17.3 Objectives:
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Describe how Earth’s tectonic plates result in many geologic features
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Compare & contrast the 3 types of plate boundaries and the features associated with each
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Generalize the processes associated with subduction zones
17.4 Objectives:
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Explain the process of convection
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Summarize how convection in the mantle is related to the movements of tectonic plates
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Compare and contrast the processes of ridge push and slab pull
Vocabulary
17.1
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Continental drift
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Pangaea
17.2
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Isochron
Magnetic reversal
Magnetometer
Paleomagnetism
Seafloor spreading
Key Concepts
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The matching coastlines of continents on opposite sides of the Atlantic Ocean suggest that the continents were once joined
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Continental drift was the idea that continents move around on Earth’s surface
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Wegener collected evidence from rocks, fossils, and ancient climates to support his theory
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Continental drift was not accepted because there was no explanation for how the continents moved or what causes their motion
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Studies of the seafloor provided evidence that the ocean floor is not flat and unchanging
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Oceanic crust is geologically young
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New oceanic crust forms as magma rises at ridges and solidifies

17.3
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17.3
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Convergent boundary
Divergent boundary
Rift valley
Subduction
Tectonic plate
Transform boundary
Ridge push
Slab pull
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As new oceanic crust forms, the older crust moves away from the ridges
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Earth’s crust and rigid upper mantle are broken into large slabs of rock called tectonic plates
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Plates move in different directions and at different rates over Earth’s surface
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At divergent boundaries, plates move apart. At convergent boundaries, plates come together. At transform boundaries, plates slide horizontally past each other
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Each type of boundary is characterized by certain geologic features
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Convection is the transfer of energy via the movement of heat matter
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Convection currents in the mantle result in an energy transfer between Earth’s hot interior and cooler exterior
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Plate movement results from the processes called ridge push and slab pull
Replace each italicized word with the correct vocabulary term
1.) Plate tectonics is the name given to the single continent that exist 200 million years ago
2.) Continental fracture is the idea that continents now separated by an ocean were once attached
3.) The process in which tectonic plates sink back into the mantle is called divergence
4.) A boundary where 2 plates come together is a transform boundary
5.) A divergent boundary with a continent forms a trench
Match each of the following phrases with a vocabulary term from the study guide
6.) A line on a map that denotes crust that formed at the same time
7.) The process that creates new ocean crust by the upwelling of magma at ocean ridges
8.) The study of the history of Earth’s magnetic field

9.) A device that measures magnetism
10.) Which suggested to early cartographers that the continents were once joined? a.
Ocean depth b.
Position of south pole c.
Shape of continents d.
Size of Atlantic Ocean
11.) What was Wegener’s hypothesis called? a.
Seafloor spreading b.
Plate tectonics c.
Continental drift d.
Slab pull
12.) The weight of a subducting plate helps pull it into a subduction zone in which process? a.
Slab pull b.
Ridge push c.
Slab push d.
Ridge pull
13.) Which is a convergent boundary that does not have a subduction zone? a.
Oceanic-oceanic b.
Oceanic-continental c.
Continental-continental d.
Transform
14.) Generally, what is the age of oceanic crust? a.
The same age as the continental crust b.
Younger than the continental crust c.
Older than the continental crust d.
Science has never determined its age
15.) Which observation was not instrumental in formulating the hypothesis of seafloor spreading? a.
Magnetization of the oceanic crust b.
Depth of the ocean c.
Thickness of seafloor sediments d.
Identifying the location of glacial deposits
16.) How fast do plates move relative to each other? a.
mm per day

b.
cm per year c.
meters per year d.
cm per day
17.) What process creates deep-sea trenches? a.
Subduction b.
Magnetism c.
Earthquakes d.
Transform boundaries
18.) Which is not a force causing plates to move? a.
Ridge push b.
Slab pull c.
Volcanism d.
Convection
19.) Continental drift was not widely accepted when it was first proposed because a.
Wegener couldn’t explain why or how the continents moved b.
Continental landmasses were too big to move slowly over Earth’s surface c.
Magnetic and sonar data proved that Wegener’s hypothesis was incorrect d.
Mantle convection currents weren’t in motion at that time
20.) Compared to ocean crust near deep-sea trenches, crust near ocean ridges is _____________ and _______________
21.) What is interesting about the magnetic pattern of ocean-floor rocks on both sides of an ocean ridge?
22.) How does new ocean crust form?
23.) Features found at divergent boundaries include a.
Ocean ridges b.
Deep-sea trenches c.
Crumpled mountains d.
Island arc volcanoes

24.) In the computer simulation we did earlier, why was a line of volcanoes created on the coastline of a continental plate when it converged with an oceanic plate?
25.) What do continental-continental plate collisions produce?
26.) During which type of boundary is crust neither destroyed nor formed?
27.) What is the driving force behind the movement of tectonic plates and where does it occur in the
Earth’s interior?
28.) What is the source of frequent volcanism near mid-ocean ridges?
29.) Write down the geological features that are formed as a result of different plates
(oceanic/continental) converging/diverging/transforming with one another