Question 1

Regions of the sea floor with negative magnetic anomalies were formed during times when Earth's magnetic field ________.

Accepted Answer

Negative magnetic anomalies on the sea floor are formed when rocks on the ocean floor solidify and align with the direction of Earth's magnetic field. When the magnetic field reverses, the rocks solidifying at that time will have the opposite alignment, resulting in negative magnetic anomalies. Therefore, the correct answer is D) had reversed polarity.

Question 2

Marine magnetic anomaly belts run parallel to ________.

Accepted Answer

Marine magnetic anomaly belts are formed due to the alternating polarity of Earth's magnetic field. They are observed parallel to mid-ocean ridges, which is where new oceanic crust is formed through volcanic activity.

Question 3

Regions of the sea floor with positive magnetic anomalies were formed during times when Earth's magnetic field ________.

Accepted Answer

Positive magnetic anomalies occur when the sea floor was formed during periods of normal polarity, meaning the magnetic field direction was the same as it is today.

Question 4

Earth's magnetic reversals are likely due to ________.

Accepted Answer

The answer of Earth's magnetic reversals are likely due to...

Question 5

Spreading rates along mid-ocean ridges have ________.

Accepted Answer

Spreading rates along mid-ocean ridges have changed through time and today vary between 1 and 10 cm/yr. While there have been variations in spreading rates over geologic time, the current range of spreading rates along mid-ocean ridges is relatively narrow.

Question 6

By deep-sea drilling,the Glomar Challenger proved the theory that if the model of seafloor spreading was correct,then seafloor sediment should be ________ and ________ as one moves away from the spreading axis.

Accepted Answer

As one moves away from the spreading axis, seafloor sediment becomes thicker due to the accumulation of more sediment over time, and older because it has been accumulating for a longer period since it was formed at the spreading axis.

Question 7

All basalts younger than 700,000 years old ________.

Accepted Answer

Basalts younger than 700,000 years old have normal magnetic polarity, which means they have the same magnetic orientation as the current magnetic field of the Earth. This is because the Earth's magnetic field regularly reverses polarity, and the age of the basalt can be determined by its magnetic orientation relative to the current field. Reverse polarity would indicate an older age. The other choices are incorrect as basalts are commonly found both on the ocean floor near mid-ocean ridges and on continents.

Question 8

According to the figure below,marine magnetic anomalies lay roughly ________ to mid-ocean ridges.

Accepted Answer

The answer of According to the figure below,marine magnetic anomalies...

Question 9

Marine magnetic anomalies result from seafloor spreading in conjunction with ________.

Accepted Answer

Marine magnetic anomalies are created when molten rocks solidify at the mid-ocean ridges and record the Earth's magnetic field at the time of solidification. When the magnetic field reverses, the new magnetic orientation is recorded in the rock, creating a magnetic anomaly. These polarity reversals occur in conjunction with seafloor spreading, which is why marine magnetic anomalies are used to study the process of plate tectonics. Choice A and B are not related to the creation of marine magnetic anomalies, and choice D is a result of the Earth's rotation and magnetic field, but not directly related to seafloor spreading.

Question 10

Consult the figure below.Marine magnetic anomaly belts are widest when and where ________.

Accepted Answer

Marine magnetic anomaly belts are the result of seafloor spreading, where new oceanic crust is formed at mid-ocean ridges and spreads outwards. The width of the anomaly belts corresponds to the rate of seafloor spreading. When spreading rates are relatively rapid, the anomaly belts are wider. Therefore, option B is the correct answer.

Quiz 3: Drifting Continents and Spreading Seas