Mt. St. Helens Volcanic Ashfall Eruption
This activity was selected for the On the Cutting Edge Exemplary Teaching Collection
Resources in this top level collection a) must have scored Exemplary or Very Good in all five review categories, and must also rate as “Exemplary” in at least three of the five categories. The five categories included in the peer review process are
- Scientific Accuracy
- Alignment of Learning Goals, Activities, and Assessments
- Pedagogic Effectiveness
- Robustness (usability and dependability of all components)
- Completeness of the ActivitySheet web page
For more information about the peer review process itself, please see http://serc.carleton.edu/NAGTWorkshops/review.html.
This page first made public: Jun 7, 2017
Skills and concepts that students must have mastered
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Description and Teaching Materials
On May 18, 1980, Mt. St. Helens in the state of Washington exploded in a cloud of ash, plus lava and mud flows. What had been a beautiful symmetrical snow-covered mountain with heavily forested slopes became a startling landscape of ash, mud, and downed trees surrounding a broken, irregular peak. Geologists had been monitoring the mountain, and access to the area was restricted; still, 63 people were killed by the eruption, including a geologist who had been observing from a nearby ridge. The ash cloud reached 19 km (12 miles) into the atmosphere, where strong east winds scattered it across numerous states and cities.
In this exercise, students receive a map of the northwestern United States and illustrations of the ash cloud in map view at hourly intervals. These drawings show the changing size and shape of the ash cloud after the eruption. Students trace the outlines of the ash cloud on a separate sheet of paper, one superimposed upon another, making a composite image. Then they lay the tracing over the map to see where the ash was carried.
The exercise is completed by answering a series of questions, which can include cities affected, velocity of ash movements, possible effects of ash on people and their activities, and comparisons with other ashfall eruptions.
Mt. St. Helens Volcanic Ashfall Instructions (Acrobat (PDF) 434kB May30 17)
Mt. St. Helens Map (Acrobat (PDF) 578kB May30 17)
Mt. St. Helens Ash (Acrobat (PDF) 186kB May30 17)
Mt. St. Helens Volcanic Ashfall Key (Acrobat (PDF) 620kB May30 17)
Teaching Notes and Tips
One of the difficulties students sometimes experience is comprehending the concept of superimposing the various shapes of the ash cloud to produce a composite drawing. A more thorough explanation of the process was added to the general description of the activity to address this problem.
Possible questions for the exercise in addition to or in place of the ones in the accompanying teaching material include the following: Which city affected by the ashfall would likely have the thickest (thinnest) accumulation of ash? Describe three ways that ashfalls affect people's health. Describe three ways ashfalls affect society in general. How does the Mt. St. Helens ashfall of 1980 compare with ashfalls in other times and places (may specify ashfalls to check: Long Valley Caldera 760,000 years ago; Yellowstone Caldera 665,000 years ago; Glacier Peak 14,500 years ago; Mt. Mazama 7600 years ago; Vesuvius in 79 CE; Novarupta in 1912; Eyjafjallajökull in 2010)?
Note that students need access to a printer to complete this exercise, as they must print some of the accompanying teaching materials.