North Seattle Community College's
PHYSICAL GEOLOGY 101
Yellowstone National Park
PLATE TECTONICS EXERCISE
@2002 -- The information contained in this document
No reproduction may be made without prior approval from the author.
I. Tracking Plate Movements using Hot Spots
As discussed in our textbook, the velocities of tectonic
plate movements have been calculated in several ways over the last 40 years. Recent
satellite technology allows us to determine precise distances and changes in distances on
extremely fine scales of time and space. We can determine current plate movements
for most areas of the globe.
In order to calculate AVERAGE plate movements over longer
periods of time, we must rely on other methods. The record of magnetic field
reversals in oceanic lava flows can be converted to a time clock by matching the pattern
of magnetic changes in these rocks with the same pattern (radiometrically dated) in
basalts erupted on land. By using magnetometers on ships, scientists do not need to
dive down and collect seafloor specimens to test and to date; instead the magnetic record
on the seafloor can be determined from simple ship-board measurements. By knowing
times and distances, we can then calculate how fast the seafloor has spread away from
divergent plate boundaries.
Another major means of calculating plate velocities is
tracking the volcanic "footprints" of hot spots as tectonic plates move across
them. We assume that a "hot spot" originates from a relatively stationary
source deep within the Earth's mantle. As plates move, these deep-seated plumes
"burn" new spots on the plates. These spots might be volcanic islands in
the ocean or volcanic landforms on continents.
The hot mantle plume is like a lit match. Hold a piece
of paper over it and it will begin to burn a hole in that paper. Move the paper
slowly and the match will burn a series of holes in the paper, the oldest "burn"
being the one farthest away from the match. The "age" of the burns and
their distance from the match can tell us how fast the paper has moved over it. P.S.
DON'T TRY THIS AT HOME.
The Hawaiian Islands, the Galapagos Islands, and Yellowstone
National Park are examples of "hot spots." In this activity we will use
readily available information for each of these geologic paradises in order to estimate
how fast three specific tectonic plates have moved over the time of the last millions of
This lab exercise this week has 15 questions.
The first five questions are worth
2 points each; the last 10 questions are worth 3 points each for a possible
40 POINTS TOTAL. Use the submission form in your In Box
in order to send in your answers.
II. Hawaiian Islands Hot Spot:
The following geology lesson, images and activities are
being used (with permission) from "A Teacher's Guide to the Geology of Hawaii
Volcanoes National Park" (copyrighted by the Hawaii Natural History
Association). It has been modified extensively for use in our GEL 101 class.
- While visiting Hawaii in the 1960's, Tuzo Wilson, one of the
founders of the theory of plate tectonics, noticed some interesting features about ocean
islands. On a map of the Pacific basin, he found three linear chains of volcanoes and
submarine volcanoes (seamounts). As shown below, these are the (1) Hawaii Islands
-Emperor Seamounts; (2) The Pitcairn Island - Tuamotu Group; and (3) the Macdonald
Seamount - Austral Group. Notice that the eastern most island or seamount of each
chain is volcanically active.
- As we can see, although separated by thousands of miles, the
three linear chains are parallel to each other. Of the three, the Hawaii-Emperor
seamount chain was the most well known. Wilson reviewed the reports that had been
published on these island chains and recorded the age of each island in the Hawaiian
chain. An interesting pattern emerged. For each chain, the islands become progressively
younger to the southeast. The extreme southeast end of each chain is marked by active
- Wilson proposed that the Hawaiian islands formed successively
over a common source of magma called a hot spot. The Island of Hawaii is currently located
above the hot spot.
Hot, solid rock rises to
the hot spot from greater depths (see the sketch below). Due to the lower pressure at the
shallower depth, the rock begins to melt, forming magma. The magma rises through the
Pacific Plate to supply the active volcanoes. The older islands were once located above
the stationary hot spot but were carried away as the Pacific Plate drifted to the
Eruptions of Hawaiian Volcanoes: Past, Present, and Future: U.S. Geological
Survey General Interest Publication.
HOT SPOTS AND MANTLE PLUMES
An Activity by Steve Mattox
- Directions: Use the map and the following information
to determine the rate of motion of the Pacific Plate over the Hawaiian hot spot. The
volcano that formed the Island of Niihau is 4.89 million years old.
The following 5 questions are worth 2 points
- Rate is the distance
traveled over a period of time. The distance
traveled is equal to the distance from the present location of the hotspot (southeast
Hawaii) to Niihau. Time is the age of the island.
- Question #1
- Start by measuring the distance from southeast Hawaii to
Niihau. Use the scale on the map. The distance is ________________ km.
- Question #2
- To determine the average rate of motion for the Pacific
Plate, divide the distance to Niihau by the age of the island. The rate of plate
movement is _____________________ km/Ma (kilometers per millions of years).
- Question #3
- Convert your answer to cm/yr (centimeters per
year). The rate of Pacific Plate movement is _____________ centimeters per
- Question #4
- Using this rate, how far will the Pacific Plate move in 50
- Question #5
In what direction is the Pacific Plate traveling? Explain. _________________
This next activity determines the average rate that the
Pacific Plate has moved over the last 65 million years.
The ages of the islands and seamounts increase with distance
away from the Hawaiian hot spot. This table shows these ages and distances for
islands and seamounts in the Hawaiian - Emperor chain.
Island Distance (km) Age
------ ------------- ---
Suiko 4,860 65
Koko 3,758 48
Midway 2,432 28
Necker 1,058 10
Kauai 519 5
Determine the average rate of plate motion over a much longer time
period. Notice that the island of Midway is quite a distance
away from the current Hawaiian hot spot. Using the same
procedure as above, calculate the average rate of plate motion on this
longer timescale. As determined from your work, this rate is
__________________ kilometers / million years. Convert your answer to cm/yr (centimeters / year): __________________
Has the Pacific Plate been moving slower or faster over the last 5 million years than it
has in the past? The rate (and direction!) of plate movement can
vary over time. Explain why this might happen. ______________________
The trajectory of plate motion points toward Hokkaido on the northern part of the Japanese
Island chain, 6,300 km (3,900 mi) away. A subduction zone offshore of Japan consumes
the Pacific plate, which is partly melted to create the volcanoes of Japan. If the
"Plate Tectonic Express" operates without change, the Big Island of Hawaii will
be headed down the Japanese trench. How long will it take Hawaii to reach Japan?
Show your work. _______________________________
III. Galapagos Islands:
The Galapagos Islands are part of another volcanic island
chain formed by passing over a hot spot. Use the figures in Chapter 1 and Chapter 11
of our textbook to determine on which tectonic plate the Galapagos Islands are found.
The Galapagos Islands are found on the _______________ plate which is traveling in the
Find the islands of San Cristobal and
Fernandina on a map of the Galapagos Islands. Click here to view a
Knowing the direction of plate movement, which of these two islands would you think is the
younger and which is the older? Why? _____________________
The Plate Tectonic story of the Galapagos is
nicely presented and illustrated on a website by Dr. Robert Rothman. Please click here
and read this short article. From the information in this article, we can
calculate the rate of movement for this particular tectonic plate.
By reading the article above, we find that the ages of the islands of San Cristobal and
Fernandina are _________ and ____________. Using the map we linked to above, the distance between these two islands is ___________
How fast is this plate moving? Show your work. Give your answer in centimeters
per year. _____________
How long will it take before the Galapagos Islands to go down the trench off of South
America's west coast? (You will need to look up some distances online or on a map in order
to calculate this) _________________
IV. Yellowstone National Park:
Hot spots may occur on continental lithosphere as well as
oceanic lithosphere. For example, Yellowstone National Park is a huge volcanic
caldera (collapsed summit of a volcanic cone) which we believe had a culminating eruption
some 600,000 years ago. This is only the latest in a series of major caldera-forming
eruptions that have traveled across the pacific northwest during the last 16 million
years. In fact, we can track the movement of this still-active volcanic hot spot as
it has shifted from Oregon through Idaho (creating its Snake River Plain Volcanic
Province) into Wyoming. Click here
to view this track (click on the link to "Detail of Calderas" on that website
for an even closer view).
In actuality, the hot spot is stationary. It is the
North American plate which is moving across it. How fast is the plate moving?
We can apply the same method as before in order to calculate this rate. Study the
map on the following link (U.S.G.S.
VOLCANO HAZARDS FACT SHEET: Yellowstone: Restless Volcanic Giant) to determine
the distance from the current hot spot to the 12.5 million year old Bruneau-Jarbridge
Caldera in southern Idaho.
From the Yellowstone Hot Spot calculation, how fast is the North American plate
moving? Show your work. Give your answer in centimeters per year.
In what direction is the North American plate moving? Explain how the Yellowstone
hot spot shows this? Where do we expect the hot spot to be in another 12.5 million