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Flashcards in Chapter 7 Study Guide Deck (17):
1

Lesson 1: The Continental Drift Hypothesis

What evidence supports continental drift?

1) the continents appear to fit together like pieces of a puzzle
2) climate clues, like sediments in glaciers in South America, Africa, India, and Australia
3) fossils of same or similar organisms were found on different continents
4) mountain ranges on different continents had common origins

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Lesson 1: The Continental Drift Hypothesis

Why did scientists question the continental drift hypothesis?

Wegener couldn’t explain what forces made the continents move.

3

Lesson 1: The Continental Drift Hypothesis

Who was Alfred Wegener?

Alfred Wegener was a German scientist who proposed the the theory of Pangaea and the continental drift hypothesis.

4

Lesson 1: The Continental Drift Hypothesis

What is Pangaea?

Pangaea is a theory suggesting that all the continents were once a huge supercontinent.

5

Lesson 1: The Continental Drift Hypothesis

What is continental drift?

Continental drift is a hypothesis which suggests that the continents are constantly moving on Earth’s surface.

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Lesson 2: Development of a Theory

What is seafloor spreading?

Seafloor spreading is a process by which new oceanic crust forms along a mid-ocean ridge and older oceanic crust moves away from the ridge.

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Lesson 2: Development of a Theory

What evidence is used to support seafloor spreading?

1) the magnetic minerals in rocks from the seafloor showed that oceanic rust forms at mid-ocean ridges and is carried in opposite directions
2) sediment collected from the seafloor can be dated and so it showed that the sediment closest to the ridge was youngest and the sediment farthest from the ridge was oldest

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Lesson 2: Development of a Theory

What is an echo sounder and what is its purpose?

An echo sounder is a device that produces sound waves that travel from a ship to the seafloor and back. It’s purpose is to measure the depth of the seafloor.

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Lesson 2: Development of a Theory

What is a topographic map?

A topographic map is a map showing land features and formations from a top-down view.

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Lesson 2: Development of a Theory

Who would use a topographic map?

Hikers, campers, survivalists, land developers, erosion specialists, and the military would use a topographic map.

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Lesson 2: Development of a Theory

What is a contour line?

A contour line is a line joining points of equal elevation on a surface.

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Lesson 2: Development of a Theory

What is an interval on a contour map?

An interval on a contour map is the difference in elevation represented by each contour line.

13

Lesson 2: Development of a Theory

What is an abyssal plain?

An abyssal plain a plain that is far away from the mid-ocean ridge.

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Lesson 2: Development of a Theory

What are two ways that mountains form?



1) Lots of lava could erupt from the center of the ridge, cool, and build up around the ridge
2) Or, as the lava cools and forms new crust, it can crack. Then rocks move up or down along the cracks in the seafloor, which forms jagged mountain ranges.

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Lesson 2: Development of a Theory

What is normal polarity?

Normal polarity is a state in which magnetized objects, such as compass needles, will orient themselves to point north.

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Lesson 2: Development of a Theory

What is magnetic reversal?

Magnetic reversal occurs and the magnetic field reverses direction.

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Lesson 2: Development of a Theory

What is reversed polarity?

Reversed polarity is a state in which magnetized objects would reverse direction and orient themselves to point south.