Florida Science Grade 6

Section 2: Seafloor Spreading

Seafloor Spreading

1.
How do scientists use sound waves to figure out the shape of the ocean floor?
A)The longer it takes a sound wave to return to the ship, the more shallow the water is.
B)The longer it takes a sound wave to return to the ship, the deeper the water is.
C)The less time it takes a sound wave to return to the ship, the deeper the water is.
D)The longer it takes a sound wave to return to the ship, the colder the water is.
2.
Why was the discovery of no rocks older than 2 billion years old on the ocean floor so important?
A)This evidence proved that the rocks on the seafloor were older than rocks on continents.
B)This evidence proved that new seafloor features are constantly being added due to continental drift.
C)This evidence proved that new seafloor features are constantly being added due to reversals of Earth's magnetic field.
D)This evidence proved that new seafloor features are constantly being added due to seafloor spreading.
3.
How do scientists explain the formation of underwater mountain ranges?
A)continental drift
B)convection currents
C)seafloor spreading
D)strike-slip faults
4.
What is a magnetic field reversal?
A)when Earth's magnetic field leaves the south pole and enters the north pole
B)when Earth's magnetic field suddenly disappears for short periods of time
C)when Earth's magnetic field leaves the north pole and enters the south pole
D)when Earth's magnetic field suddenly runs east/west instead of south/north
5.
What tool does a scientist use to detect magnetic fields?
A)a magnetogram
B)a thermometer
C)a fieldometer
D)a magnetometer
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