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Week 3: Sample Week A Volcano Hypothesis and Analyses
Last week you did PBL Steps 1-6. This reading provides sample responses that someone could have made after reading the Volcano Scenario and applying the ESS and PBL approaches.

In Week 2 you were to read and analyze the Volcano Scenario (PBL Step 1), which contains an event and situation that tie together the ESS and the PBL Model approaches of the course. Step 2 of the PBL Model is to list hypothesis , ideas, or hunches. You were to focus your hypothesis, ideas, or hunches around the volcano event you read about in the scenario.

Here is an example hypothesis, idea, or hunch relating to the Volcano Scenario you worked with in Week 2:

Hypothesis
A volcano affects the Earth's systems by releasing extreme heat from Earth's core; changing the shape of the land (lithosphere), the quality of the air (atmosphere), the form and quality of the water (hydrosphere); and destroying plants and animals (biosphere). I do not believe an eruption of Mt. Rainer would have the same overall effect as did Mt. Pinatubo since Mt. Rainier is a composite volcano in the Cascade Range like Mt. St. Helen's; therefore, its eruption should cause results similar to the Mt. St. Helen's eruption of 1980 rather than Mt. Pinatubo.

Step 3 of the PBL Model is to list what is known. You were to list what is known in the form of an Earth system science analysis. You were not supposed to do any research at that point. You were to list what you knew and include reasons from your own thinking, education, and experience.

Below are some examples of Earth system science interaction statements from the Volcano Scenario:

Volcano Event to Sphere Interactions

E > A
Volcanic gases, including water vapor, are released into the atmosphere. We know that water vapor comes from ground water heated by magma because of the geysers at Yellowstone.

As in previous great eruptions, large quantities of dust and ash would be added to the atmosphere, and the dust could be carried in the upper winds and spread out in the upper troposphere. The additional dust added to the atmosphere could produce more brilliant sunrises and sunsets as it did after the eruption at Krakatoa in 1883.


E > B
The eruption would impact the biosphere by resulting in death for some animals and providing an opportunity for others. Death would come in many ways, including from the initial blast itself, the impact of falling material, burying/smothering/clogging by ash, burning, toxic gases, reduction in light, and encroachment of organisms "fleeing" into already populated areas.

Volcanic ash can be very rich in some cases and could enrich the lands around the blasted area as was seen after the 1980 Mt. St. Helen's eruption.


E > H
As with Mt. St. Helen's, the heat of the eruption would melt vast quantities of ice that would flow down existing stream valleys causing extensive flooding.

The hydrosphere is impacted primarily in two ways. The most obvious is that water bodies receive large amounts of volcanic ash and debris. The second is that the heat and wind generated, increases evaporation. Evaporation in combination with water vapor expelled by the volcano increases local rainfall.


E > L
The lithosphere is replenished by a volcanic eruption. A volcanic eruption is the active rearrangement of part of the lithosphere. Volcanic material is jettisoned to the surrounding countryside resulting in the deposition of volcanic ash and pieces of the mountain itself onto the surrounding topsoil.

As with Pinatubo, large amounts of ash and dust would accumulate on the land surrounding the volcano.

L > E
A volcanic eruption is part of the lithosphere. Tectonic plate interactions are behind the volatile nature of the lithosphere and the cause of volcanic eruptions.

Before and during an eruption, seismic activity increases. Earthquakes are common, often coming in swarms. An earthquake was thought to cause the landslide that caused the Mt. St. Helen's eruption of 1980.


Sphere to Sphere Interactions

A > B
Carbon dioxide and sulfur dioxide may lead to acid rain. Increased acidity can act as a mechanism to ruin plant growth as well as life in surrounding rivers, streams, and ponds.

Toxic gases released by the volcano and possibly a local decrease in oxygen concentration may result in death.


A > H
The hydrologic cycle would temporarily increase. Heating of the atmosphere by the eruption would result in increased evaporation. Eventually water vapor from evaporation and from the volcano would fall as sulfuric acid rain due to sulfides expelled during the eruption.

Falling ash and acid rain could cause a change in the pH of surface water and possibly the groundwater.


A > L
There will be more erosion because of increased rainfall, such as the mudslides in California that resulted from the excessive rain of El Niņo.

Winds could cause the blowing and drifting of ash as it does with sand or snow.


H > B
Additional flows of sediment-laden water could continue to rebury new plants that start to grow.

Life depends on water. With the water containing ash, the remaining animals will have little to drink.


B > L
The lithosphere will be impacted as old growth forests are swept away in the flood waters, exposing fragile soils that will then rapidly erode.

With the limited amount of vegetation remaining after the blast, potential erosion could take place.

L > B
Ash is added to the topsoil and increases fertility. I notice that many crops are grown on the sides of volcanoes because of the rich soil.


L > H
There will be increased turbidity in streams and lakes as eroded material is deposited. Erosion deposits changed the creek near my house to a more pond-like environment.

The erosion deposits may change the chemical composition of the water, just as dumping pollutes the water.

Causal Chains

E > H > L > B
As with Mt. St. Helen's, the heat of the eruption would melt vast quantities of ice. During the pre-eruption of a snowcapped mountain, a noticeable meltdown of the snow due to the increase in internal heat occurs. This meltdown will increase the water flow into small streams, creeks, and rivers. As the snow cover continues to melt, it eventually will pick up more dirt, mud, and debris from the runoff. The larger the amount of ice available to melt, the larger the potential mud flow that wipes out living things in its path.

E > L > A > H > B
Tephra, or volcanic ash, will be carried downwind and will fall to produce a deposit that covers a broad area, including rivers, streams, and oceans. The resulting silt will affect turbidity and oxygen-carbon dioxide cycles. This in turn will affect the biosphere and lithosphere as the silt filters through and is deposited on the ocean bottom.

At this point you are done reading the individual assignment sample responses. To read the sample questions and problem statement from the Volcano Scenario's team assignment, click here.

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