BACKGROUND:
Volcanic eruptions occur continuously around the
world. They have also occurred throughout geologic time. The Earth has been
restless since it was created 4.5 billion years ago, so we can assume that
volcanoes were a basic building unit of the original Earth. Volcanoes were
and are important to the development of the Earth. Lava produced the crust
when the Earth was forming. Volcanoes also produced much of the Earth’s
water. Hydrogen and oxygen chemically combined inside the Earth, and the
resulting water molecules "outgassed" from volcanoes as steam into
the atmosphere.
The Post Lab is a research activity. The students will
find recent eruptions listed in reference material or on the Internet. They
will then plot their findings on a classroom map. The pattern that they will
find is that most volcanoes are created at diverging and converging plate
boundaries.
As described in the Pre Lab background, most volcanoes
occur at convergent or divergent plate boundaries, and at a few intraplate
settings. Only convergent boundaries where subduction (one plate sinks
beneath another, creating much magma) produce volcanoes. Convergent
boundaries where collisions take place produce little magma. Divergent plate
boundaries probably have the most volcanic activity in the world, but most
of these are located within the oceans, and are unknown. Intraplate
volcanoes are caused by hotspots, and can occur anywhere.
There are many ways to format this assignment.
Enclosed is an example of how the students can collect the data from their
reference material. Alternatively, you may want the students just to find
locations on a map, and not to copy all the information down.
PROCEDURE:
- Review the settings of volcanoes with the class.
- Give the class their assignment. Have each group of students find 3-5
volcanoes in the library or on the Internet. You may want to assign
particular geographic areas to different students or student groups. If
you assign Internet research, here is a site to start with or have
students conduct their own search.
http://www.geo.mtu.edu/volcanoes/
Michigan Technological University - volcano sites from around the world.
- Have each student group share their information with the rest of the
class. Have the students plot their findings on the classroom map. If
you are using the relief map, make sure that the students notice that
volcanoes are usually on mountainous areas, but that not all mountains
are volcanoes.
The students will notice that volcanoes are more abundant in the
circum-Pacific region and the Mid-Atlantic Ridge area. These are
primarily convergent and divergent settings, respectively. However your
students will have also have plots of areas like Hawaii, that are
intraplate volcanoes. Explain that these do not fit the plate tectonic
model for the formation of volcanoes, but are still fairly well
understood by geologists.
