Name _______________________________
Lab # __________________
HOT SPOTS
The Earth’s lithosphere (crust and rigid mantle) is broken into numerous plates. These plates are situated on a
partially melted and moving asthenosphere (plastic mantle). In areas where the asthenosphere is hot, magma rises
and diverges causing ridges. In area where the asthenosphere is colder, magma sinks causing a trench at a
convergent plate boundary. These convection currents in the mantle cause the continents to drift and is the driving
force behind the earthquakes that occur on Earth.
The exceptions to this rule are hot spots. Hot spots form from magma plumes that originate deeper in the Earth
below the asthenosphere. The location of the hot spot remains stationary and the crust slowly moves over the hot
spot. As the crust moves over the hot spot, volcanic islands can form in a chain formation as shown below. The
island currently over the hot spot is an active volcano. The islands to the right are used to be over the hot spot and
were active volcanoes that have since moved and become dormant. You can tell the direction of plate motion by
drawing an arrow from the active volcano to the oldest volcano.
Using the idea that chains of volcanic islands are formed as a crustal plate moves over a hot spot in the mantle, it
is possible to calculate the average speed at which the crustal plate is moving. The following diagram illustrates
the eight main islands of the Hawaiian chain. The approximate age is given for the larger islands.
1. Using the scale shown in the diagram, determine the distance between the five major islands and enter your
answers in the appropriate spaces on the following data table.
Measure the distance between the dots placed at the center of the major islands.
2. Convert each distance from kilometers to centimeters by multiplying the value in kilometers by 100,000.
Enter the new data in the appropriate spaces on the data table.
3. Calculate the approximate age differences between the islands and enter the data in the table.
Islands
Distance Between the
(In kilometers)
Two Islands
(In centimeters)
Difference In Approximate
Ages of the Two Islands
Hawaii and Maui
________________km
_________________km
_________________km
Maui and Molokai
________________km
_________________km
_________________km
Molokai and Oahu
________________km
_________________km
_________________km
Oahu and Kauai
________________km
_________________km
_________________km
4. Using the following formula, calculate the approximate speed at which the crustal plate was moving
between the times that each of the islands formed. Enter your data in the following data table.
Speed of crustal =
Movement (cm/yr)
Distance between the two islands (in centimeters)
Difference in approximate age of the two islands (in years)
Islands
Approximate Speed of Crustal Movement Between
the Times That the Two Islands Formed (cm/yr)
Hawaii and Maui
______________ centimeters per year
Maui and Molokai
______________ centimeters per year
Molokai and Oahu
______________ centimeters per year
Oahu and Kauai
______________ centimeters per year
5. Now calculate the average speed of crustal movement.
** Average speed of crustal movement = ______________ centimeters per year.
After completing this activity, answer the following questions:
1.A. In which direction was the crustal plate apparently moving during the time that the Hawaiian Islands were
formed? ________________________________________________________________________
____________________________________________________________________________________
B. Explain your answer._______________________________________________________________
____________________________________________________________________________________
2. A. According to your data, did the crustal plate always move at the same speed? _________________
_______________________________________________________________________________
B. Explain your answer. ______________________________________________________________
_______________________________________________________________________________
Name: _________________________________________
Questions 1 through 5 refer to the following:
Diagram I below is a map showing the location and bedrock age of some of the Hawaiian Islands. Diagram II is a
cross section of an area of the Earth illustrating a stationary magma source and the process that could have formed
the islands.
1) Which of the Hawaiian Islands had the greatest probability of having a volcanic eruption?
1) Hawaii
2) Maui
3) Kauai
4) Oahu
2) Which graph best represents the ages of the Hawaiian Islands comparing them from point A to point B?
3) Volcanic activity like that which produced the Hawaiian Islands is usually closely correlated with
1) frequent major changes in climate
3) nearness to the center of the ocean
2) frequent earthquake activity
4) sudden reversals in the Earth’s magnetic field
4) Compared to the continental crust of North America, the oceanic crust area of the Hawaiian Islands is probably
1) thicker and different in composition
3) thicker and similar in composition
2) thinner and similar in composition
4) thinner and different in composition
5) If each island formed as the crustal plate moved over the magma source in the mantle as shown in diagram II,
where would the next volcanic island most likely form?
1) southeast of Hawaii
3) northeast of Hawaii
2) between Hawaii and Maui
4) northwest of Kauai