Download How Can Hot Spots Help Determine Rate and Direction of Plate

How Can Hot Spots Help Determine Rate and Direction of Plate Movement?
Name:
Date:
Purpose: To use information about the formation and age of the Emperor Seamount and
Hawaiian Island chain to determine the rate of movement of the Pacific Plate.
Background: Most volcanoes form along divergent boundaries or near subduction zones;
however, the Hawaiian Islands are examples of intra-plate volcanism associated with a hot spot.
A hot spot is a stationary area of upwelling heat in the mantle. Hot magma rises through cracks
in the crust and forms a volcano. The Hawaiian Islands are located near the middle of the Pacific
plate. If the plate did not move, there would only be one volcano over the hot spot. However, as
the Pacific plate moves, the old volcanoes move with the plate and new areas of crust are
exposed to the hot spot, allowing new volcanoes to form. The result is a chain of seamounts and
islands with the youngest island over the hot spot. Geologists can use the ages and distances
between islands to calculate rates of plate movement and determine the direction that the Pacific
Plate has moved over time.
The attached map shows the Hawaiian Island-Emperor Seamount Chain.
1. Describe the pattern formed by the islands and seamounts on the Pacific Ocean floor.
2. Notice the bend in the chain. Where does it occur?
Explain what a bend in the chain could mean in terms of the movement of the Pacific Plate
over time.
The list below gives the names of islands and seamounts that are part of the Hawaiian chain,
their distances from the hot spot (currently located below the volcano Kilauea on the “big island”
of Hawaii), and their ages.
Distance from
Age (million
Island or Seamount
Hot Spot (km)
years old)
Kilauea, Hawaii
0
0.0
West Maui
221
1.3
Kauai
519
5.1
Nihoa
780
7.2
Necker
1058
10.3
Le Perouse Pinnacle
1209
12.0
Laysan
1818
19.9
Midway
2432
27.7
Abbott Seamount
3280
38.7
Daikakuji Seamount
3493
42.4
Koko Seamount
3758
48.1
Jingu Seamount
4175
55.4
Nintoku Seamount
4452
56.2
Suiko Central
4860
64.7
Graphing Data
Make a graph of the data, plotting “Age” on the horizontal (x-) axis and “Distance from Hot
Spot” on the vertical (y-) axis. Make the short side of the graph paper the x-axis. The range of
data for both axes should start at 0. Use a scale of 1 inch (10 small boxes) = 10 my for the x-axis
and 1 inch = 500 km for the y-axis. Plot all the points. Label the following points: Kilauea,
Kauai, Laysan, Midway, Abbot, Koko and Suiko. Draw TWO best-fit lines on the graph, one
between Kilauea and Laysan and one between Laysan and Suiko. Give the graph a title.
3. Look at the graph. The slope of a line tells you the rate (or speed) of plate movement. Based
on the slope of the best fit lines, does the Pacific Plate appear to have moved at a constant
rate or has it changed over time? Give evidence for your answer, referring to specific times
and distances on the graph.
Calculating Rate of Plate Movement
4. Calculate the rate (speed) of plate movement between the two islands based on the
information in the chart. Use the following formula:
Rate = (distance of island 1 - distance of island 2)
(age of island 1- age of island 2)
Calculate answers to 1 decimal place. Include units. SHOW YOUR WORK.
Suiko to Koko
Abbot to Midway
Laysan to Kauai
Kauai to Kilauea
5. Based on the calculations above, what happened to the rate of movement from 65 million
years ago until the present?
It (circle one): increased/decreased/remained constant.
6. Convert the rate for Kauai to Kilauea into cm/year. (1 km = 100,000 cm) Show your work.
7. Look at the map. A new volcano is starting to form over the hot spot. This new volcano will
be (N, S, E, W, SE, NE, SW, NW) (circle one) relative to the location of Kilauea.
8. Based on the map and the ages of the island, in what direction was the Pacific Plate moving
when the first seamounts formed?
9. Based on the data and map, when did the change in direction of plate movement occur?
(Hint: find the seamounts closest to the bend in the chain and look at the chart for their
ages.)
10. Look at a map of Tectonic Plates. What type of plate boundary is located along the north
edge of the Pacific Plate? (Be specific.)
If the
Pacific Plate continues to move in the same direction, what may happen to the northernmost
seamounts in the Emperor Seamount chain? Explain your answer in terms of plate
movement.
Map of Hawaiian Islands and other islands and seamounts of the Hawaiian-Emperor chain,
shown with 1- and 2-km bathymetric contours. (Data from USGS Professional Paper 1350.)