Plate Tectonics and People

How Big is Big? Part II: Eruptions

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Myth: The eruption of Mt. St. Helens in 1980 was enormous! Just huge!

Fact: The 1980 eruption of Mt. St. Helens wasn't even close to some of the biggest eruptions in human recorded history as measured by the volume of ejected material. Compared to some prehistoric eruptions, it was actually pretty small.

In the following problem set, you will use data from the VOGRIPA program, which is run by the British Geological Survey, to compare some past eruptions of various volcanoes. There are two main questions to ask when comparing eruptions:

  1. How much material was erupted? and
  2. How explosive was the eruption?

These, and others, are the questions you'll answer in this problem set.

Problem Set



For this assignment, you will need to record your work in a word processing document. I'm not giving you a worksheet this time. It is up to you to construct your own document.

Go to the main page of the Volcano Global Risk Identification and Analysis Project (VOGRIPA). Find information about the eruptions for the volcanoes listed below. You can find each of these volcanoes by using the SEARCH tab. When you click the SEARCH tab you will get taken to a new page. Just scroll down a little way down the page and type the name of the volcano in, don't change anything else, then press the Submit button. Some volcanoes in my list have lots of documented eruptions. I've given you the dates of the ones I want you to look at.

  • Sierra la Primavera (95,000 BP)
  • St Helens (1980)
  • Kilauea (1790)
  • Eyjafjallajökull (2010)
  • Pinatubo (1991)
  • Vesuvius (79)
  • Krakatau (1883)
  • Tambora (1812)
  • Fernandina (1968)
  • Redoubt (1989)
  • Toba (74,000 BP)

Make some kind of a table to store useful information about these eruptions. Specifically you will want to know the type of volcano, the composition of the eruption, the eruption magnitude, and the bulk volume.

Answer these follow-up questions:

  1. Which eruption in this activity was the largest in terms of explosivity and which was the largest in terms of volume?
  2. Where does the 1980 eruption of Mt. St Helens rank among all the eruptions in this activity? How about the 79 AD Vesuvius eruption? Are you surprised by these results?
  3. Describe the correlation (if any) between the type of volcano and the magnitude of its eruptions.
  4. Which volcanoes in this activity are the most active in terms of the numbers of number of confirmed eruptions?
  5. You may have to look at a map for this one. Can you tell which volcanoes are hot spot volcanoes and which ones are subduction zone volcanoes? What are the clues besides looking at a map that will tell you.
  6. Discuss whether there is a relationship between type of lava, magnitude of eruption, and volume of eruption for the volcanoes in this exercise. Feel free to supplement with other volcanoes if it helps to make your point. Perhaps it will help to make some plots for this one. It also may help to refer back to lesson 5 in which we discussed the characteristics of different types of lava and their compositions and viscosities relative to each other.

Submitting your work

Save your word processing document as either a Microsoft Word or PDF file in the following format:

L6_eruptions_AccessAccountID_LastName.doc (or .pdf).

For example, former Cardinals manager and hall of famer Red Schoendienst would name his file "L6_eruptions_afs2_schoendienst.doc"

Hang on to your document because you will need it for part 2 of this problem set.

Grading criteria

I will use my general grading rubric for problem sets to grade this activity.