The Creeping Hot Spots
Students learn about the Mantle Plume Theory, plate tectonics, and Idaho geography by experimenting with a map of Idaho.
- Students will be able to explain the basics of the Mantle Plume Theory.
- Students will understand that the crust slides over the mantle.
- Students will be able to name key cities and geologic features of Idaho.
Other geologic phenomena require a combination of theories to be explained. For example, events creating the Snake River Plain that stretches across southern Idaho from Oregon to Wyoming cannot be described as easily as the San Andreas fault. A combination of "Rifting," "Basin and Range Faulting," "the Mantle Plume Theory," and Plate Tectonics are required to explain that big crescent. For a concise description of these theories and the likely sequence of events that made the Snake River Plain see pages 2.1 to 2.5.
The student activity that follows will require that you understand the basics of these theories.
- One copy of the enclosed map of Idaho for each student
- Magic marker or highlighter for each student
- Candle and match (for teacher)
- One small Snickers candy bar for each student (optional)
- Maps of Idaho and neighboring states
With the Idaho map you will demonstrate the Mantle Plume Theory, Rifting, and Plate Tectonics. The students will then repeat the demonstration on their own maps individually and in teams, adding information to their maps as they work.
Part 1 - Demonstrate Rifting
Locate the Western Snake River Plain on your map and weaken the area by punching several pencil holes through paper "crust." Then use your fingers to tug at the paper and create small tears and -voila- you've created a rift valley.
As another way of demonstrating the process you may give each student a Snickers bar and let them pull and twist it to create faults and fractures before they eat it. You may wish to do this at the end of the class. Perhaps the Snickers bar could be used as a reward for demonstrating their knowledge to you about the formation of the Snake River Plain and geography of Idaho.
Part 2 - Demonstrate the Great Rift
Part 3 - Demonstrate Mantle Plume Theory
Light the candle to symbolize the hot spot. Hold the crust (your map of Idaho) over the stationary candle high enough so that it won't scorch. From your reading of 2.1 to 2.5 you know that the Mantle Plume Theory applies only to the Eastern Snake River Plain and that 10 million years ago the Plume was located under what is now Twin Falls. You also know that the North American Plate has crept southwest over the eons and that 600,000 years ago the Plume or hot spot was active under Yellowstone.
As you describe this to the kids, lower the Twin Falls area to just the point of scorching and slowly move the crust (the map) southwest to form the Eastern Snake River Plain between Twin Falls and Yellowstone. You or a student can say, "10 million years ago, 9 million years ago," and so on as you slowly move the paper over the candle toward Yellowstone so that by the time you get there you're at "one million years ago." Let the scorching paper represent the creation of the Eastern Snake River Plain.
Part 4 - Student Maps
|Directions||Rivers and Places|
|East||Yellowstone National Park|
|West||Craters of the Moon Nat'l Monument|
|North||Grand Teton National Park|
|Towns and Cities||Western Snake River Plain|
|Arco||Eastern Snake River Plain|
|Idaho Falls||States and Countries|
Note: Make sure the students understand that the above geologic processes happened concurrently over millions of years and that this explanation is a simplified version of reality.
The Creeping Hot Spots