BACKGROUND:
Mt. Shasta is in northern California, part of the
Cascade Range. Studies by geologists show that Mount Shasta has erupted 10
or 11 times during the last 3,400 years and at least 3 times in the last 750
years. Mount Shasta does not erupt at regular intervals, but its history
suggests that it erupts at an average rate of once every 600 year during the
last 4,500 years. Future eruptions could develop from vents at or near the
present summit. In the picture above, a second cone, called Shastina can
also erupt.
The type of eruption would most likely be explosive.
Explosive eruptions can produce volcanic ash, pyroclastic flows, and lateral
blasts. Non-explosive eruptions, can also develop after the initial eruption
and form lava flows and domes. Both types of eruptions can cause mudflows
down local drainage, and both types often are accompanied by gas emissions.
PROCEDURE:
- Discuss the information on Mt. Shasta with the
class. Show the students the slides of dangers associated with a volcano
(see below). If you project the picture large enough, have students
"walk" amongst the rubble.
- Show the slides that illustrate the following
terms. At this point, you are just exposing the students to the terms.
They should not attempt to memorize them.
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
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.
Pyroclastic flows = streams of hot ash and rock
fragments that are mixed with hot air and other gases. 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
Landslide = a downhill flow of rock debris on the
side of a volcano
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