Activity Overview
Students investigate the connections between volcanoes and the Earth system by
considering the widespread distribution of volcanic material that enters the
atmosphere. In particular, students explore the connections between winds and
volcanic ash transport. This relationship is important for solving the Chapter
Challenge, since the ability of volcanoes to affect regions of the United States depends upon the transport of airborne material. Students draw upon their knowledge of the
relationship between magma composition and properties of the magma developed
in Activity 2 to better understand why some volcanoes erupt explosively with
widespread, sometimes global effects, whereas others erupt quietly and locally. Students also explore some of the most famous recent examples of volcanic eruptions.
Scale is a very important concept in understanding the Earth system. This
investigation gives students the chance to explore the scales and categories of volcanic eruptions. It also gives students the chance to make inferences from data (maps and data tables). Specifically, they should make inferences about the importance of
knowing wind direction when thinking about what parts of the country might be affected by a volcanic eruption. They should also be aware that the pattern of ash
dispersal could be complicated by variations in wind direction and speed with height in the atmosphere. A full appreciation of this would require a good understanding of the circulation of the atmosphere.
Preparation and Materials Needed
The investigation requires no special preparation.
Materials
Think About It
Student Conceptions
The question explores students’ conceptions of how far volcanic ash can travel. To this point in the chapter, students have examined flows. The largest lava flows in recorded history are small in scale compared to the area affected by volcanic ash. They may not be willing to admit that volcanic ash could ever reach their community, particularly if they live east of the Mississippi River.
Some students will consider what they learned in Activity 1 and factor this into
their thinking. For example, if they found a volcano within a certain distance of
their community, they may note that ash and dust might reach their community. If they live in a volcanic region, they might point out particular types of flows that can reach their community. Some students believe that volcanic ash can travel around the globe. Few high school students will think of the gases and water vapor that emerge from a volcano as “material,” and such materials are certain to eventually reach
their community.
Answer for the Teacher Only
Refer to the last paragraph of the Background Information. If the students live
anywhere in the western United States, they are likely to realize that they are within reach of an ash fallout from an explosive eruption in the Pacific Northwest, although the upper-level winds would have to be in the right direction. If they live in the
eastern United States, much farther from the likely location of the eruption, there might still be fallout of very fine ash, but unless the eruption is of a size comparable to or greater than such uncommon eruptions as Tambora or Krakatoa, the ash would be very small in volume and would be detectable only by careful observation. The
probability of an explosive volcanic eruption in the United States elsewhere than in the Pacific Northwest is with just a few exceptions (e.g., Yellowstone) extremely small, because the geologic setting is one of stable continental crust rather than a
subduction plate boundary. If upper-level winds are moving in the right direction,
they can transport ash from eruptions of volcanoes in Mexico to portions of the United States. |