Chapter 4: Problem 16

Why are the marine magnetic anomalies bordering the East Pacific Rise in the southeastern Pacific Ocean wider than those bordering the Mid-Atlantic Ridge in the South Atlantic Ocean?

Short Answer

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The marine magnetic anomalies bordering the East Pacific Rise in the southeastern Pacific Ocean are wider than those bordering the Mid-Atlantic Ridge in the South Atlantic Ocean due to the differences in seafloor spreading rates. The East Pacific Rise has a faster spreading rate, causing the oceanic crust to move away more quickly and resulting in wider bands of marine magnetic anomalies. In contrast, the Mid-Atlantic Ridge has a slower spreading rate, leading to narrower bands of anomalies.

Step by step solution

Understanding Marine Magnetic Anomalies

Marine magnetic anomalies are bands of alternating high and low magnetic intensity found on the seafloor. They are a result of the Earth's magnetic field interacting with the newly created oceanic crust at mid-ocean ridges. As new crust is formed and moves away from the ridge, it records the Earth's magnetic field direction. When the Earth's magnetic poles reverse, the direction of the magnetic field recorded in the rocks changes. This creates a pattern of alternating magnetic bands parallel to the mid-ocean ridge.

Identifying Seafloor Spreading Rates

The seafloor spreading rate is the speed at which new crust is created and moves away from the mid-ocean ridge. It differs between various mid-ocean ridges. The East Pacific Rise has a much faster spreading rate than the Mid-Atlantic Ridge. This means that oceanic crust moves away from the East Pacific Rise more quickly than it does from the Mid-Atlantic Ridge.

Relating Spreading Rates to Marine Magnetic Anomaly Width

The width of marine magnetic anomalies is directly related to the seafloor spreading rate and the duration of magnetic pole reversals. As spreading rate increases, each magnetic anomaly band moves away from the ridge more quickly. If the time interval between magnetic pole reversals stays constant, a faster spreading rate will result in wider bands of marine magnetic anomalies.

Comparing Anomaly Widths Between East Pacific Rise and Mid-Atlantic Ridge

Since the East Pacific Rise has a faster spreading rate than the Mid-Atlantic Ridge, the marine magnetic anomalies bordering the East Pacific Rise in the southeastern Pacific Ocean are wider than those bordering the Mid-Atlantic Ridge in the South Atlantic Ocean. This difference in width can be attributed to the different seafloor spreading rates.

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Why are the marine magnetic anomalies bordering the East Pacific Rise in the southeastern Pacific Ocean wider than those bordering the Mid-Atlantic Ridge in the South Atlantic Ocean?

Short Answer

Step by step solution

Understanding Marine Magnetic Anomalies

Identifying Seafloor Spreading Rates

Relating Spreading Rates to Marine Magnetic Anomaly Width

Comparing Anomaly Widths Between East Pacific Rise and Mid-Atlantic Ridge

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