Further Reading / Supplemental Links
Vocabulary
abyssal plains Very flat areas that make up most of the ocean floor.
bathymetric map A map of the seafloor created from the measurement of water depths.
echo sounder A device that uses sound waves to measure the depth to the seafloor.
mid-ocean ridge The location on the seafloor where magma upwells and new seafloor
forms. Mid-ocean ridges are the dominant feature of divergent plate boundaries found
in the oceans.
seafloor spreading The mechanism for moving continents. The formation of new seafloor
at spreading ridges pushes lithospheric plates on the Earth’s surface.
trench A deep hole in the seafloor where subduction takes place. Trenches are the deepest
places on Earth.
Points to Consider
- How were the technologies that were developed to fight World War II used by scientists
for the development of the seafloor spreading hypothesis? - In what two ways did magnetic data lead scientists to understand more about conti-
nental drift and plate tectonics? - How does seafloor spreading provide a mechanism for continental drift?
- The features of the Atlantic Ocean basin are described in terms of seafloor spreading
and continental drift. Now look at the features of the North Pacific Ocean basin and
explain them in those terms as well.
6.4 Theory of Plate Tectonics
Lesson Objectives
- Describe what a plate is and how scientists can recognize its edges.