Download 15 - Crustal Speed

Name ___________________________________
Date _________________
Lab Period _____
Lab Day ______
Crustal Speed
Complete the chart
Islands
Distance in km
Use map scale
Distance in cm.
km X 100,000
Age Difference in years
subtract
Hawaii and
Maui
Maui and
Molokai
Molokai and
Oahu
Oahu and
Kauai
Average
XXXXXX XXXXXXX XXXXXXXX
Speed
In cm/yr
Questions: Answer questions # 1 – 3 in complete sentences.
1.
2.
3.
4.
A
B
C
D
5.
A
B
C
D
6.
A
B
C
D
7.
A
B
C
D
8.
A
B
C
D
Lab # 15 Crustal Speed
Introduction:
Most scientists believe that the earth’s crust is broken into pieces, much like the cracked
shell of a hard-boiled egg. These pieces are called crustal plates and are thought to be
moving across the mantle, the layer of earth directly below the crust.
The diagram below illustrates how some scientists believe lines of volcanic islands are
produced as superheated molten material rises upward from deep within the mantle. The
molten material breaks through weak places in the crustal plates as the plates move over
the top of the stationary hot spot (or plume) in the mantle. In the diagram, the first
volcano is the oldest; the second and third are progressively younger. The fourth volcano
in the diagram is directly over the hotspot, is the youngest, and is still active.
Using the concept of volcanic island being formed over a stationary hot spot, it is
possible to calculate the crustal speed.
PROCEDURE:
The following diagram shows the eight main islands of the Hawaiian chain.
Approximate age is given for the larger islands.
Using the scale shown on the diagram, determine the distance between the five major islands
and enter the answers on the answer sheet in the data table. Measure the distance between the
dots placed at the center of the major islands.
Convert the distances from kilometers (map scale) to centimeters by multiplying the value in
kilometers by 100,000 (1000 m/km and 100 cm/m). Enter the new value for distance in the data
table.
Calculate the approximate age differences between the islands and enter the data in the data
table. You must subtract.
Using the following formula, calculate the approximate speed at which the crustal plate was
moving between the times that each of the islands formed.
Speed of crustal movement
(cm/yr)
=
Distance between the islands (in cm)
_______________________________________
Difference in ages of the two islands (years)
Calculate the average speed of the Pacific Plate.
QUESTIONS:
1.
In which direction was the crustal plate (Pacific) moving when the Hawaiian Islands were
formed? Explain your answer.
2.
A new Hawaiian Island is currently forming. Predict the location of the newest Hawaiian
Island.
3.
According to your data, did the crustal plate always move at as constant speed? Explain
your answer.
Use the map of the Hawaiian Islands to answer questions #4 through #6.
4.
Why is Niihau Island much smaller than “The Big Island” of Hawaii.
A.
The are more people on Hawaii than Niihau
B.
The hot spot was much stronger when Niihau formed than when Hawaii formed
C.
The hot spot was much stronger when Hawaii formed than when Niihau formed
D.
Niihau is older and has been worn away by waves
5.
Predict the age of Niihau.
A.
3,000,000 years
B.
3,500,000 years
C.
4,000,000 years
D.
4,500,000 years\
6.
If waves wear away (erode) the islands, where might you expect to find extinct volcanoes
that are under water?
A.
North of Hawaii
B.
East of Maui
C.
Northeast of Oahu
D.
Northwest of Niihau
7.
According to the map on page 5 of the Earth Science Reference Tables, which direction
is the South American Plate moving?
A.
Northeast
B.
Northwest
C.
Southeast
D.
Southwest
8.
According to the map on page 5 of the Earth Science Reference Tables, which direction
is the African Plate moving?
A.
Northeast
B.
Northwest
C.
Southeast
D.
Southwest