AnswersMO-Earth and Space Science APlate Tectonics

Characteristics of the Seafloor Answers

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1
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Which type of material becomes molten rock at subduction zones?

A
light plates
B
heavy plates
C
continental crust
D
new oceanic crust
2
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When scientists analyzed drilling samples from the Glomar Challenger study, which discovery did they make about rocks in relation to a mid-ocean ridge?

A
Rocks closer to the ridge are newer.
B
Rocks closer to the ridge contain more iron.
C
Rocks farther from the ridge are denser.
D
Rocks farther from the ridge are more jagged.
3

Why do rocks on the ocean floor form a pattern of magnetized stripes?

A
The rocks contain iron that points in the direction the rocks move away from the ridge.
B
The rocks are composed of different materials depending on when they formed.
C
The rocks change shapes as a result of the pushing and pulling of seafloor spreading.
D
The rocks contain iron that points in different directions depending on Earth's polarity.
4

Which is the first step in the seafloor spreading process?

A
A crack forms in oceanic crust.
B
Volcanoes erupt under the ocean.
C
Molten rock rises up through the crust.
D
Dense plates are subducted under less dense plates.
5

Which statement describes the cyclic nature of seafloor spreading?

A
Continents are created.
B
New oceanic crust is created.
C
Volcanoes erupt and remove crust.
D
Old crust gets thicker at subduction zones.
6

Which statement accurately describes one aspect of plate tectonics that involves subduction and seafloor spreading?

A
Older crust is melted at subduction zones.
B
Crust is created at the coastlines of continents.
C
Continents do not move as a result of seafloor spreading and subduction.
D
Crust is created as the mantle hardens under the lithosphere.
7

Which evidence originally supported Hess’s idea of seafloor spreading in 1968?

A
Younger rocks are closer to mid-ocean ridges.
B
The destruction of crust occurs at deep-sea trenches.
C
Oceanic rocks are pillow-shaped when formed.
D
Rocks across the ocean floor have alternating magnetic stripes.
8

How do magnetic stripes of iron in ocean rock provide evidence of seafloor spreading?

A
They show when Earth's poles reversed.
B
They show how the density of the seafloor has changed.
C
They reveal a matching pattern on either side of the ridge.
D
They reveal differences in the mineral composition of newly created rock.
9

How does oceanic crust move along mid-ocean ridges?

A
away from dense crust
B
parallel to the ridge
C
away from the ridge
D
under less dense crust
10

Which information did the Glomar Challenger study in 1968?

A
the rate of seafloor spreading
B
the direction of seafloor spreading
C
the age of rocks in various places in the ocean
D
the contents of rocks in various places in the ocean

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