Plate Tectonics Review Answers

Plate Tectonics Review Answers

1. Plate Tectonics Review Questions

1. What is plate tectonics in your own words?
The Earth’s crust is broken into pieces called “Lithospheric Plates” that “float” over top the
asthenosphere. These plates move relative to one another as magma circulates underneath. As the
plates move, they affect one another by placing stress along the boundaries. Plates exhibit 3 types of
motion; they can divide, collide, or slide past each other.

2. What are the three types of plate boundaries?
a. Divergent b. Convergent c. Transform

3. What kind of motion would be expected at a convergent plate boundary?
The plates move together – squeezing the rock and/or making the rock sink back down into the mantle.

4. Generally, how fast is the motion of the plates? 2-3 cm per year or 1 inch per year

5. What kind of motion would be expected at a transform fault boundary?
The plates slide past and along each other horizontally.

6. What drives the motion of the plates?
Heat from the core of Earth is being transferred to the colder surface. As this material circulates inside
the asthenosphere (hotter material moves toward the crust and colder material moves toward the
core), the solid lithosphere moves along with the convection currents.

7. What is the name of the process that occurs at the mid ocean ridge?
Sea – Floor Spreading (SFS)

8. What kind of motion would be expected at a divergent boundary?
The plates are dividing and moving apart from one another

9. Describe what may become of the East African Rift Valley in millions of years.
The rift valley is caused by tension along a divergent boundary. Over time, the valley will continue to
widen and separate eventually forming a new ocean with a mid-ocean ridge at the center.

10. What is happening to Iceland?
Iceland was built along the mid-Atlantic ridge and is separating about 1 inch per year. The island is
being built from an east to west direction.

11. What is going on in the middle of the Atlantic Ocean?
Sea-Floor Spreading is creating a mid-ocean ridge widening the Atlantic Ocean.

12. On average, in ten years, how much bigger will the Atlantic Ocean be? About 10 inches

13. How could two plates moving in the same direction cause a transform fault?
A fracture zone along a mid-ocean ridge has different rates of spreading. The area between two
spreading areas could be moving horizontally opposite to each other as a result.

2. Plate Tectonics Review Questions

14. What is the situation at the San Andreas Fault?
San Andreas Fault is Located in California where the North American and Pacific Plate interact. The
Pacific Plate is moving faster to Northwest sliding past the North American Plate. This causes
earthquakes in California.

15. What are the three possible types of convergences that can occur when two tectonics plate collide with
one another?
a. Oceanic-Oceanic b. Oceanic-Continental c. Continental-Continental

16. Complete the following chart…
Boundary Type of Crust Resulting Feature Examples
Divergent
Oceanic-Oceanic Mid-Ocean Ridge
Mid Atlantic Ridge
East Pacific Ridge
Continental-Continental Rift Valley
Iceland
East African Rift
Convergent
Oceanic-Continental
Ocean Trench
Volcanic Mountains
Peru-Chile Trench
Andes Mt.
Oceanic-Oceanic
Ocean Trench
Volcanic Island Arc.
Marianas Trench
Japan
Caribbean Islands
Continental-Continental Mountain Range
Appalachian Mt.
Himalayan Mt.
Transform
Continental-Continental Strike Slip Fault San Andreas Fault
Oceanic-Oceanic Fracture Zone
Mid – Atlantic Ridge
Fracture Zone

17. How would the behavior of two plates that are said to be along a convergent boundary best be
described?
The plates are colliding and moving together, if one plate is more dense than the other subduction will
also occur allowing one plate to slip underneath of another.

18. During Oceanic-continental convergence, which plate sinks into the mantle? Why does it do this?
The oceanic plate will sink into the mantle because ocean crust is more dense than continental crust.

19. Define the word “Subduction.”
Subduction refers to the movement of one plate below another due to differences in density. The more
dense plate will sink into the mantle and the less dense plate will float overtop.

20. Explain how oceanic-oceanic convergence differs from oceanic-continental convergence.
Both convergences produce similar features, however, each will produce a different type of volcano.
The oceanic to oceanic produce volcanic island arcs, while the oceanic-continental will produce volcanic
mountain ranges each with a different type of magma.