Download Hawaiian Continental Drift

THE HAWAIIAN ISLANDS & CONTINENTAL DRIFT
Name: _________________________
Background
As you well know, the Hawaiian islands are located far
away, near the middle of the Pacific Ocean, 4,000 km
(2,500 miles) from the nearest continent. The Hawaiin
islands are rather young landmasses and did not
originate during the breakup of Pangea into Gondwana
and Laurasia, or subsequent breakups.
Rather, the Hawaiin islands are volcanic in origin, and
as you have learned, the age of volcanic ash or rock
can be determined using radioactive dating methods.
More specifically, this metamorphic rock contains
radioactive potassium isotopes that decay into the more
stable argon gas.
In the following activity, you will you use your knowledge of radioactive dating to learn
about the rate of continental drift while developing a deeper understanding of the
tectonic activity that has lead to the development of the Hawaiian islands. This activity
will also prepare you for further activities where you will come to a deeper
understanding of speciation and the adaptive radiation that has occurred on these
islands.
Procedure & Questions
Surf to http://pubs.usgs.gov/publications/text/hotspots.html.
1. Describe J. Tuzo Wilson’s “hotspot” theory. What prediction does it make about the
Hawaiian islands?
2. How are ancestral Hawaiian myths consistent with this theory of the origin of the
islands?
Use the following graph relating the percent of parent or original potassium to its age, to
determine the age of the volcanic rock associated with each of the main Hawaiian
islands. Record your answers in the table provided.
Hawaiin
Island
Main
Volcano
Parent
Material
(K)
118.8
Daughter
Material
(Ar)
1.2
Hawaii
Mauna Kea
Maui
117.6
2.4
Oahu
Haleakal
(Red Hill)
Waianae
114.0
6.0
Kauai
Kauai
111.6
8.4
Nihoa*
Nihoa
109.2
10.8
Necker*
Necker
106.8
13.2
% of
Parent
Material
Age
(MYA)
*Are not currently Hawaiian island but mountains below sea level.
3. Is this data consistent with the Wilson’s hotspot theory? Explain.
4. Based on your knowledge of the age of the islands, in which direction is the plate
moving through which the hotspot is acting? Explain.
5. Is there a pattern to the height of the volcanoes on the Hawaiian islands as reported
on the map on the following page? Why would this pattern exist based on your
knowledge of the age of the islands?
If we now assume that the hotspot theory is correct, a few easy steps will allow you to
determine the rate of movement of the pacific plate.
6. Assuming that the hotspot that is currently under Mauna Kea on Hawaii has not
moved, use the scale on the map above to determine how far each islands midpoint
has traveled from the hotspot (Mauna Kea). Fill in the age of each island again too.
Hawaiin
Island
Hawaii
Maui
Main Volcano
Mauna Kea
Distance
(km)
-
Oahu
Haleakala (Red
Hill)
Waianae
Kauai
Kauai
Nihoa*
Nihoa
775 km
Necker*
Necker
1050 km
Age (Millions
of Years)
7. Using the distance from Mauna Kea to Necker and the age of Necker, calculate the
average speed at which the plate on which the Hawaiian islands exist has been
moving in centimeters per year (hint: convert km to cm, and millions of year to years
before calculating). Show your work. Does this rate seem slow?
8. Using the data from the previous table, construct a graph (x-axis = Distance in km, yaxis = Age in millions of years). Label your data points with the island names.
9. Based on the graph, does it appear that the plate movement has been consistent
over the past 10 million years? Explain.
10. What does the pacific ridge, in the picture to the
right, suggest about this movement?
Post Homework Discussion Question
1. Assuming that the islands of Maui and Kauai were the exact same height as Hawaii is
today, calculate how many millimeters of height have been lost on both islands.
Then, using those answers and your knowledge of the time that has elapsed since
these islands have formed, and how many millimeters of height has been lost per
year on both islands.
2. Necker island is currently 100 m above sea level, and is estimated to have been as
high as 1000 m in the past. Using this information and the age of the Necker Island,
alculate how many millimeter of height has been lost per year.
3.