Plate Tectonic - Hazards (3)
Pre Lab 

  • Exploring different volcanic eruptions.
  • Experimenting with ash eruptions.
  • dormant
  • eruption
  • extinct

Students evaluate the hazards of different volcanoes.

The 1980 eruption of Mt. St. Helens, Washington. 


Many hazards are associated with volcanic eruptions. In this lab, students will consider the following dangers:

Volcanic ash = small particles of the magma that are blown out of the volcano. They are carried away by the wind, along with volcanic gases. They land on the Earth’s surface, creating layers that may be several feet in thickness. This may cause buildings to collapse.

Volcanic gases = gases emitted by a volcano either alone or along with ash or lava. Volcanic gases consist chiefly of water vapor, carbon dioxide, carbon monoxide, and various compounds of sulfur, chlorine, and other elements. None of these are breathable!

Ash flows = streams of hot ash and rock fragments that are mixed with hot air and other gasses. Together these form a fluid which rapidly flows down the side of a volcano.

Lava flow = a "river" of lava that moves downhill and can crush, burn, and bury structures

Mud flow = a mass of water-saturated rock debris that moves downslope as a fluid. Previously deposited ash often makes up part of a mudflow.

Landslide = a downhill flow of rock debris on the side of a volcano

Volcanoes erupt differently, depending on the composition and thickness of the erupting lava, the amount of gas in the parent magma, and force of the eruption. Volcanoes that erupt lava that is low in silica and gases tend to be "quiet," mostly pouring out streams of fairly fluid lava. Kilaeua volcano in Hawaii is a good example. Volcanoes that erupt silica-rich magmas, and that have a lot of gas, tend to be explosive. This produces tremendous clouds of volcanic ash, ash flows, and gasses. The loose material produced by these eruptions often becomes the raw material for landslides or mudflows.

Mt. St. Helens, Mt. Etna, and Kilauea are active volcanoes. Mt. Vesuvius and Mt. Lassen are sleeping (dormant) volcanoes; they erupted at some point in the past (1912 for Mt. Lassen, 1944 for Mt. Vesuvius). They were dangerous in the past, and will probably erupt and be dangerous again in the future.

  1. Show the students the slides from the volcanoes set. Use these slides to illustrate the kinds of damage that volcanoes can produce. Emphasize that lava flows, ash flows, mud flows, etc. can all occur. As you look at the slides, ask your students what damage was caused by the eruptions, or what might happen in future eruptions. Tell students to record the "dangers" they see on their lab sheets.
  2. In the second part of the lab, students create their own volcanic disaster and record what happens. They will need the volcano that they made for PLATE TECTONICS -VOLCANOES (3) LAB. Have the students make a village near the volcano. Instruct them to use sand to represent an ash flow. Tell them to gently pour sand until the "cone" becomes unstable and flows down the side of the model, as shown below. Ask the students to keep track of the amount of sand they use. They should realize that it takes a lot of "lava" or "ash" to create a flow. Make sure the students also note students that there is a "critical point" at which the sand begins to slide and then moves very quickly. We suggest that you do this activity either in a tub or on newspaper that can capture the sand in order to reuse it.

    This exercise helps the students to see that an ash flow will bury everything in its path. They should record their observations by drawing a "before" and "after" picture.

    Exercise 1:
    Mt. St. Helens - lava flows, landslides, ash flows, mudflows, ash, and gasses.
    Mt. Vesuvius. - similar to Mt. St. Helens
    Mt. Etna - lava flows, gasses
    Mt. Lassen - similar to Mt. St. Helens
    Kilaeua - lava flows

[Back to Plate Tectonic Grid]
  [Back to Hazards (3)]