Seafloor Spreading

Mid-ocean Ridge, NASA: Public Domain

In this topic, you learned about how scientists used sonar to map the ocean floor, which helped them to discover seafloor spreading at mid-ocean ridges.

Like large mountain ranges, these ridges run through three of the major oceans. You also learned that the seafloor spreads at a rate of 0.5 to 4 inches per year.

Finally, you learned about the occasional reversal of the Earth's magnetic field and that scientists found evidence of these reversals stored in minerals of basaltic rock.

Thanks to these findings, scientists elevated the theory of seafloor spreading into plate tectonics, which you will explore in the next topic.