Educational worksheet on seafloor spreading with multiple-choice corrections for students.

1. During the 1940s and 1950s, scientists began using sonar on moving ships to map large areas of the ocean floor in detail.
2. The youngest rocks are found near the mid-ocean ridges.
3. The scientist Harry Hess proposed the theory of seafloor spreading.
4. As the seafloor spreads apart, hot seawater moves upward and flows from the cracks.
5. As the new seafloor moves away from the ridge and becomes hotter, it moves upward and forms still higher ridges.
6. The research ship Glomar Challenger was equipped with a drilling rig that records magnetic data.
7. Rocks on the seafloor are much older than many continental rocks.
8. When plates collide, the denser plate will ride over the less-dense plate.
9. Earth’s magnetic field has always run from the north pole to the south pole.
10. The magnetic alignment in rocks on the ocean floor always runs from the north pole to the south pole.