Lessons From the Sea Page Grade 5 Unit 4



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boundaries occur when two plates move away from each other. Interestingly, almost all these boundaries are under the sea. One of the few places where there is a divergent boundary between two parts of a continent is in Africa. This boundary has created the Great Rift Valley, which runs north/south through Africa, splitting apart the continent and forming the Red Sea. When the rift valley becomes deep enough, the sea will invade and divide Africa in two.

Where divergent boundaries occur under the sea, magma flows up from the cracks that are created in the Earth’s crust, forming new seafloor and widening the ocean. They may form underwater mountain ranges, like the Mid-Atlantic ridge, and deep-sea hydrothermal vents, such as those found off the Nazca plate near the Galapagos Islands. One of the fastest spreading boundaries is between the Pacific and Antarctic plates, widening both oceans as well as the ocean between Antarctica and the other continents.


Convergent and Divergent Boundaries


Reading Review Questions


  1. What are tectonic plates?

  2. When two tectonic plates move toward each other, what is the boundary where they meet called?

  3. What are three kinds of geologic formations that occur at these boundaries?

  4. What is a hot spot, and where is it found?

  5. What causes most earthquakes?

  6. What are divergent boundaries, and where are most of them found?

Lesson 1

Plate Movements Activity






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