Name____________________________________________________________________________ Date_____________________________________ Hour_____________
Determining How Fast a Lithospheric Plate Moves
According to the theory of plate tectonics, the Earth’s lithosphere, or outermost layer consisting of the crust and upper
part of the mantle, is made of interlocking pieces, much like the cracked shell of a hard-cooked egg. The pieces of the
lithosphere are known as lithospheric plates. The plates float across the surface of the hot, soft, flexible layer of mantle that
lies beneath them. This layer is called the asthenosphere.
Most of the Earth’s volcanoes are found at the boundaries of the plates. But a few volcanoes are found, surprisingly, in
the center of the plates. Such volcanoes are thought to be caused by “hot spots” located deep within the Earth – perhaps in the
lower parts of the mantle or even in the core itself. Superheated molten material rises from a hot spot and “burns through” the
plate, creating a volcano.
Because hot spots are stationary, a chain of volcanic islands may be formed as an oceanic plate moves over a hot spot.
See the diagram below. By determining when the islands in the chain were formed, it is possible to calculate how fast the plate
is moving over a hot spot. In this activity you will determine how fast the Pacific plate is moving over the hot spot that formed
the Hawaiian Islands. The Hawaiian Islands are the most recent additions to the Hawaiian chain of volcanoes, which extends
3,500km (2,175mi) northwesterly across the floor of the Pacific Ocean.
Label the diagram below.
1. ___________________________
2. ______________________________
6. _______________________________
3. ______________________________
4. ______________________________
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5. _____________________________
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7. _________________________
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8. __________________________________
9. ___________________________________
Word bank: oldest island, hot spot, moving crustal plate, oldest volcano,
youngest volcano, mantle, second oldest volcano, third oldest volcano,
youngest island
Answer these questions
10. What is the lithosphere? _______________________________________________________________________________________________________________
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11. What is the asthenosphere? ____________________________________________________________________________________________________________
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12. What is a hot spot? _____________________________________________________________________________________________________________________
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13. Using the map below and a ruler, find the distance in centimeters between each island and enter your answers into the
column titled “Measurement between dots in centimeters” in the data table below. Use the dots to measure from.
Islands
Measurement
between dots
in cm.
Distance between
the islands in
kilometers
Distance between
the islands in
centimeters
Difference in
approximate ages
of the two islands
in years
Speed of crustal
movement in
cm/yr.
Hawaii and Maui
Maui and Molokai
Molokai and Oahu
Oahu and Kauai
To find the speed of crustal movement, use the following formula.
Speed of crustal movement in cm/yr. = Distance between the two islands (in centimeters)
Difference in approximate ages of the two islands (in years)
14. What is the average speed of crustal movement? ____________________________________
15. In which direction was the crustal plate apparently moving when the Hawaiian Islands were formed? _______________________
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16. Did the crustal plate always move at the same speed? _____________________ Explain your answer. _______________________________
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