What happens when the flow in the outer core changes, and Earth's magnetic field changes direction?

A magnetic field that is opposite to the present field has ______________ polarity.

What device can detect small changes in magnetic fields?

The study of the history of Earth's magnetic field is called...

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Which major ocean-floor features were discovered by data collected by sonar and magnetometers?

What did scientists learn by matching magnetic patterns on the seafloor with known patterns of magnetic reversals on land?

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What rock evidence led to the discovery of seafloor spreading?

An imaginary line on a map that shows points that have the same age is called a(n)

The theory that explains how new oceanic crust is formed at ocean ridges, slowly moves away from ocean ridges, and is destroyed at deep-sea trenches is called

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What is true of magnetic fields?

What is an imaginary line on a map that shows points that have the same age?

What theory explains how new oceanic crust is formed at ocean ridges, slowly moves away from ocean ridges, and is destroyed at deep-sea trenches?

Studies of the seafloor provided evidence that the ocean floor is

New oceanic crust forms as _________________ rises at ridges and solidifies.

As new oceanic crust forms, the older crust moves...

Seafloor spreading can be compared to a(n)