GEOL100 Homework
Hot spot volcanism in western North America
PART 1: Rate of plate movement over the Yellowstone hot spot
This hand-out contains a physiographic map of the northern Great Basin,
showing a linear pattern of felsic volcanic centers -- the Snake River Plain
Volcanic Province. These are thought to have formed as the North America plate
moved across the Yellowstone “hot spot”, a deep source of volcanic material.
The current location of the Yellowstone hot spot is shown by the geysers, hot
springs, and other indicators of a shallow magma chamber below Yellowstone
National Park. Assume that the hot spot has been stationary during the time
period when the volcanic rocks were erupted, and that the line of volcanic
centers formed as the North American plate moved across the hot spot.
Using the map and the following information on the age of specific
volcanic centers, determine the rate of North American plate motion for each of
the intervals between the eruptions at these volcanic centers (i.e., measure
between adjacent volcanic centers, and calculate the rate of motion between each
pair) by using the formula rate = distance/time. Notice that both variables –
distance between one volcanic center and the next, and age of each volcanic
center – is a range of values rather than a unique number. There are several
possible ways to deal with this; briefly explain the method you chose (e.g., use
the average, use both extremes and average the result, etc.). Show your work,
and don’t forget to include units in your answers.
Volcanic field Age (in millions of yrs) Distance (in km) Rate
Bruneau-Jarbidge (B-J) 12.5 - 10.0 ____ ____
Twin Falls (TW) 10.0 - 8.6 ____ ____
Heise (H) 6.5 - 4.3 ____ ____
Yellowstone Plateau (YP) 2.1 - 0.6
In your report, use the map and rates to answer the following questions. (As always,
separate “observations” from “interpretations” in your report). Note: Although
it is fine to refer to a figure or chart that displays your data, you must also state
the pertinent data, in complete sentences, in your report.
What direction is the North American plate moving?
How long has it been moving in this direction?
Has the rate of motion been constant?
Should any of these volcanic centers be considered to be active (i.e.,
potentially hazardous for nearby communities)?
How much longer do you think the Yellowstone National Park area will
be active?
Where would you expect volcanic activity in the future?
Explain these answers briefly.
