Section #: 17.2
Seafloor Spreading
Practice Test
1.
The thickness of ocean sediments that are close to a mid-ocean ridge is __________ the thickness of ocean sediments that are far from mid-ocean ridges.
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a.
less than
b.
the same as
c.
more than
d.
always 100 times
Hint
2.
A __________ is a device that can detect changes in the strength of the magnetic field.
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a.
GPS
b.
magnetometer
c.
sonar
d.
satellite
Hint
3.
What is the polarity of a magnetic field that has the same polarity as the present magnetic field?
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a.
a reverse polarity
b.
a normal polarity
c.
an isochron
d.
a magnetic reversal
Hint
4.
Harry Hess' theory of __________ explained how ocean crust is generated and destroyed.
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a.
continental drift
b.
continental movement
c.
seafloor spreading
d.
plate tectonics
Hint
5.
What two topographic features of the ocean floor were discovered only with the use of sonar?
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a.
volcanic islands and mid-ocean ridges
b.
mid-ocean ridges and deep-sea trenches
c.
shallow-sea trenches and volcanic islands
d.
mid-ocean ridges and earthquakes
Hint
6.
What is the study of Earth's magnetic record?
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a.
paleomagnetism
b.
paleontology
c.
paleogeography
d.
magnetometer
Hint
7.
Rocks close to mid-ocean ridges are __________ rocks far from mid-ocean ridges.
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a.
younger than
b.
the same age as
c.
older than
d.
a different composition than
Hint
8.
What is an isochron?
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a.
a line on a seafloor map that connects points of equal age
b.
a line on a seafloor map that connects points of equal elevation
c.
a point on a seafloor map that has a magnetic reversal
d.
a part of a mid-ocean ridge
Hint
9.
What causes the seafloor to spread?
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a.
earthquakes
b.
drifting continental crust
c.
rising molten magma
d.
sinking magma
Hint
