Relative Motion
Problem:
We know that the crust is moving. How fast does the crust move? In this exercise we will attempt to
measure the rate at which the crust is moving in at least three locations in the United States.
San Andreas Fault:
Refer to the map of California illustrating the San Andreas Fault
On either side of the San Andreas Fault, geologists have identified rock units that have been split and carried
in opposite directions after their formation. One such rock unit is indicated on the map.
1. In what direction is the North American Plate moving in this location?
2. In what direction is the Pacific Plate moving in this location?
3. What has been the average annual rate (cm/yr) of movement along the San Andreas Fault over the last
25 million years?
4. If movement continues at this rate and direction, how long before the Dodgers and Giants are again
cross-town rivals?
5. This rate of movement may be considered quite small. Why do Californians face the threat of major
earthquakes?
Yellowstone: (Refer to the map of the Yellowstone Hot Spot)
Yellowstone National Park is situated over a hot spot. Most geologists believe that hot spots are stationary
plumes of hot magma rising in the mantle. As the magma reaches the surface it leads to the formation of
volcanoes. Once a volcano has moved off of the hot spot it will become inactive. The Yellowstone volcano last
erupted 600,000 years ago in one of the largest volcanic eruptions that geologists have evidence. This
volcano led geologists to coin the term supervolcano.
1. Determine the rate and direction the North American Plate has been moving in this location over the
last 17 million years.
2. Milwaukee lies 3,000 km directly east of Yellowstone. What would have to happen in order for the
Yellowstone hot spot to move directly under Milwaukee in the future?
3. If the scenario described in your answer to the last question did occur, how long before the Yellowstone
hot spot would be directly under Milwaukee?
Hawaii: (Refer to the map of Hawaii)
The Big Island of Hawaii is situated over an active hot spot. Determine the average age of each island.
4. In what direction and at what average rate (cm/yr) has the Pacific Plate been moving over the last 4.7
million years?
5. In what direction and at what average rate (cm/yr) was the Pacific Plate moving between 4.7 million
years and 1.6 million years ago?
6. In what direction and at what average rate (cm/yr) has the Pacific Plate been moving over the last 1.6
million years?
7. Has there been any change in the direction and/or rate of movement of the Pacific Plate in this area
over the course of the last 4.7 million years?
8. Where will the next (new) Hawaiian island form? Explain your reasoning.
Hawaii (the big picture):
Refer to the map, “Earth’s Fractured Surface” or “Earth’s Dynamic Crust” or a map of the World’s ocean
floor. Locate the Hawaiian Islands and the Emperor Seamounts. Locate the table illustrating the age and
distance of Hawaiian Islands and Emperor Seamounts from the Hawaii Hot Spot.
1. Provide evidence to support the following statement: “The Emperor Seamounts were formed over the
same hot spot as the Hawaiian Islands.” (think of visualizing the data)
2. Suiko is the oldest Seamount in this chain that is visible on the Pacific sea floor. When was the first
seamount created over the Hawaiian Hot Spot? (Use your maps. This is not a trick question, but it is
tricky.)
3. What happened to the Pacific Plate at about the time that the seamount of Daikakuji was formed? Be
thorough.
4. Could the Yellowstone hot spot ever move under Chicago? Explain thoroughly. Provide supporting
evidence
Hawaii (the big picture)Alternative:
Use the following website to generate the data for your own table of age vs distance.
Emperor Seamounts Website:
http://www.classzone.com/books/earth_science/terc/content/investigations/es0810/es0810page05.cfm
Scale: 1cm. = 75 km
San Francisco
Los Angeles
San Andrea Fault
25 million year old rock unit
Yellowstone Hotspot
Scale: 1 cm = 50km
Volcanic
Formation
Average Age (m.y.)
McDermitt
Owyhee/Humboldt
Bruneau/Jarbidge
Twin Falls
Picabo
Heise
Yellowstone Plateau
17
14
12
11
9
5
1
(last erupted 600,000 years
ago)
Hawaiian Islands
Scale: 1 cm = 50 km
Active Volcano
Extinct or Dormant Volcano
Center of Underlying Hot Spot
Island
Age of Identified Volcano
(m.y.)
Kauai
Oahu
Molokai
Maui
4.7
2.5
1.6
1.1
Mauna Kea last erupted 3,000 years
ago
Mauna Loa last erupted in 1984
Kilauea is active
Loihi Seamount is active
Hawaii (Big
Island)
Hawaiian Islands and Emperor Seamounts Age vs Distance from Hawaii Hot Spot
Volcano Name
Distance from Kilauea along
trend of chain (km)
Best K-Ar age
(Ma)
Kilauea
0
0-0.4
Mauna Kea
54
0.375 + 0.05
Kohala
100
0.43 + 0.02
Haleakala
182
0.75 + 0.04
Kahoolawe
185
> 1.03 + 0.18
West Maui
221
1.32 + 0.04
Lanai
226
1.28 + 0.04
East Molokai
256
1.76 + 0.04
West Molokai
280
1.90 + 0.06
Koolau
339
2.6 + 0.1
Waianae
374
3.7 + 0.1
Kauai
519
5.1 + 0.20
Niihau
565
4.89 + 0.11
Kaula
600
4.0 + 0.2
Nihoa
780
7.2 + 0.3
Unnamed
913
9.2 + 0.8
930
9.6 + 0.8
Necker
1,058
10.3 + 0.4
La Perouse Pinnacles
1,209
12.0 + 0.4
Brooks Bank
1,256
13.0 + 0.6
1,330
13.0 + 0.6
1,435
12.3 + 1.0
1,460
12.3 + 1.0
Laysan
1,818
19.9 + 0.3
Northampton Bank
1,841
26.6 + 2.7
Pearl and Hermes Reef
2,281
20.6 + 2.7
Midway
2,432
27.7 + 0.6
Unnamed
2,600
28.0 + 0.4
Unnamed
2,825
27.4 + 0.5
Colohan
3,128
38.6 + 0.3
Abbott
3,280
38.7 + 0.9
Daikakuji
3,493
42.4 + 2.3
Gardner Pinnacles
Yuryaku
3,520
43.4 + 1.6
Kimmei
3,668
39.9 + 1.2
Koko (southern)
3,758
48.1 + 0.8
Ojin
4,102
55.2 + 0.7
Jingu
4,175
55.4 + 0.9
Nintoku
4,452
56.2 + 0.6
Suiko (southern)
4,794
59.6 + 0.6
Suiko (central)
4,860
64.7 + 1.1