Earth Science: Geology, the Environment, and the Universe

Chapter 18: Volcanic Activity

Problem of the Week

Faster than a Speeding Bullet, More Powerful than a Locomotive

No, we’re not talking about Superman; we’re talking about the eruptive power of volcanoes, specifically composite volcanoes. Composite volcanoes are commonly associated with subduction zones—plate boundaries at which one plate is pulled under another. These are volcanoes that form from alternating eruptions of lava, ash, cinders, and other pyroclastic solids of varying sizes. The violent eruptions often cause widespread devastation of the surrounding area. Composite volcanoes are found along the western margins of North and South America and around the Mediterranean. One volcanic event in North America was the eruption of Mt. St. Helens in 1980. Another volcanic event—the eruption of Mt. Vesuvius—occurred in A.D. 79 in the Mediterranean.

Getting a Feel for These Two Eruptions:

Take a look at the following Web sites to get a "feel" for the devastation caused by each of these eruptions.

Mt. Vesuvius
Here you will read general descriptions of the eruption and a good explanation of the terms used to describe volcanic eruptions.

Mt. St. Helens
This site has a lot of information about the eruption taken from various news reports.

http://volcano.und.nodak.edu/vwdocs/msh/msh.html
Here you will find a series of links that discuss all aspects of this volcano.

General Information on Volcanoes
Volcano World is a good overall reference on volcanoes worldwide.

Recording some data:

Using the Web sites listed above, find the following information for each volcano. This information will be used in the Problem section. Click here for a printable chart.

Problem:

Why have the stories of these eruptions been told throughout history?

Take a look at the data you have collected. How would you rate these two eruptions? Which was most powerful? Which was most destructive? Which moved the most material into surrounding areas? Which caused the most deaths?

1. Create an "eruption scale" from 1 – 10, with 1 as the lowest and 10 the greatest on the scale.


2. How did you rate them? Mt. St. Helens? ______ Mt. Vesuvius? ______


3. Discuss your findings with other groups of students in your class and compare your ratings and the methods you used to determine the ratings


4. Following this discussion, ask your teacher to provide the Web site that shows how volcanologists rate volcanic eruptions. Compare your methods and results to theirs.