Week 1
Week 2
Week 3
Week 4
Week 5
Week 6
Week 7
Week 8
Week 9
Week 10
Week 11
Week 12
Week 13
Week 14
Week 15
Week 16


Week 3: Sample Week A Volcano Questions and Problem Statement
Earlier this week you read sample responses for PBL Steps 1-3. This reading provides sample responses that a team could have made for PBL Steps 4-6.

Step 4 of the PBL Model is to list what is unknown. You and your team were to list what is unknown about the problem posed in the Volcano Scenario. You were to do this by generating a list of questions you would like to have answered. Below are some of the questions that a team could have been generated from the Volcano Scenario in Week 2.

How do scientists predict volcanic eruptions?

[One way is to monitor seismic activity around the volcano. The first evidence of an impending eruption is usually a series of seismic events or earthquakes. In order for an eruption to occur, lava must rise from its formation zone deep underground to near the surface. The lava must literally push overlying rocks aside to rise through them. The rocks are brittle and break as they are bent and twisted, releasing seismic energy that we record as earthquakes. By placing a number of seismic recorders around a volcano, the movement of the new mass of rising lava can be followed. (http://www.cotf.edu/ete/modules/volcanoes/vmonitor.html)]

What evacuation procedures are currently in place in Washington State and the Mt. Rainier area?

[According to FEMA, most communities in the vicinity of Mt. Rainier have plans in place. For example, the Orting school district keeps the school buses at the school to evacuate the flood plain where the schools are located given enough warning.]

How do the climates and weather around Mt. Pinatubo and Mt. Rainier compare?

[Mt. Pinatubo does not have an extensive glacier system like Mt Rainier. Therefore, during an eruption of Mt. Rainier, the glacial ice would melt quickly, causing larger and more devastating lahars. Mt. Rainier's precipitation seems to be mostly in the form of snowfall. The visitor's center (at 5,500 feet) averages 575 inches of snow. In the winter of 1971-72 it received a record 1,122 inches.]

Will seasonal weather variations influence the effects of a major eruption?

[Assuming that Washington does not get as much water in as short a time as do the Philippines during their rainy season. Therefore, the physical destructive impact of an eruption of Mt. Rainier would be more limited to the acute effects of the immediate eruption. This is not to say that there would be no long-term effect. I simply don't think that the problem of lahars would pose a threat year after year. I base this on what little I know of the Mt. St. Helen's aftermath. To my knowledge, lahars did not become a chronic problem.]

What will happen to the glaciers on the top before and during an eruption and where will the water go?

[As magma builds, the ground water supply heats up, and snow and ice may melt and cause increased water flow. I wonder if this can be used to predict an eruption.]

What are lahars, what are they composed of, and where will they travel?

[LAHAR- A flowing mixture of water - saturated rock debris that forms on the slopes of a volcano, and moves downslope under the force of gravity, sometimes referred to as debris flow or mudflow. The term comes from Indonesia. Lahars occurred at Mt. St. Helen's in 1980.]

What damage did lahars cause in the Mt. Pinatubo area?

[From what I have read, much of the destruction caused from Mt. Pinatubo was caused by lahars resulting from normally heavy rainfall occurring over a four-year period. Mt. St. Helen's in 1980 ejected .25 cubic miles of volcanic material, but Mt. Pinatubo ejected a volume of 4.25 cubic miles of volcanic rock. (http://www.cotf.edu/ete/modules/volcanoes/vsizeserupt1.html)]

What are the general dynamics of these lahars? (i.e., how far do they flow, does this simply depend on rain levels, topography, etc.; do lahars simply act as a muddy glacier and eventually "disappear," and so on.)

[They can travel over 50 miles and can reach speeds of over 40 mph. Mt. Rainier has a long history of eruptions that caused lahars. About 5,800 years ago, a sudden collapse of the 16,000 foot summit sent a lahar containing over one-half cubic mile of material thundering down the White River valley. This wall of mud was 100 feet high and it buried an area of 125 square miles including the area where the cities of Kent, Sumner, Auburn and Puyallup now are located. It finally stopped beneath the waters of Puget Sound. It is known as the Osceola mudflow, one of the largest]

What is the impact of the lahars on streams and rivers?

[As Brian mentioned, lahars may choke the streams, but rivers may also direct their flow. At Mt. St. Helen's, after the outrush of the avalanche and ash cloud, enormous mudflows slid off the mountain down several of the adjacent river valleys. These flows were caused by water from blast-melted glaciers and snow that mixed with the already powdered rock to form pasty, muddy flows. These hot and cold masses of mud swept down the valleys of several rivers, sweeping away buildings, vehicles, trees, and even bridges. Trees amounting to more than four billion board feet of salable lumber were damaged or destroyed by the near-supersonic lateral blast of rock, ash, and hot gases. One of these flows even reached and blocked the shipping channel of the Columbia River, 55 miles downstream. (http://www.cotf.edu/ete/modules/volcanoes/vsituations4.html)]

How could we estimate the primary blast area that would result from a Mt. Rainier eruption?

[Using the Mt. St. Helen's eruption as a guide, all those within 5 to 10 miles of the volcano on the north side, scientist and layman alike, were doomed. Some took a few quick pictures. Then, realizing their situation, most ran or tried to drive away from the approaching cloud of dust and steam. The ash-laden cloud engulfed the area with a force sufficient to strip huge trees bare and uproot or break them off at ground level. The temperature within the cloud reached 500ºF and was sufficient to cause serious burns and start fires. The rock avalanche roared over Spirit Lake and the valley of the North Fork Toutle River, burying them under layers of rock up to several hundred feet thick. (http://www.cotf.edu/ete/modules/volcanoes/vnarrative3.html)]

What are pyroclastic flows?

[Ash flows are turbulent mixtures of hot gases and pyroclastic materials carried with such force and speed that they level anything in their paths. The French term, "nuee ardente," for "glowing cloud" is used to describe the intense heat carried through the air.]

Can the release of SO2 from the eruption cause acid rain?

[Sulfur is largely responsible for the problem of acid rain. It is oxidized into sulfur dioxide in the atmosphere that creates sulfuric acid when combined with atmospheric moisture. Nitrogen in the atmosphere oxidizes into nitrous oxides that produce nitric acid when combined with atmospheric moisture.]

What was the character of past eruptions in the Cascade chain?

[The mud flows from Mt. St. Helen's dumped more than 75 million cubic yards of sediment into rivers, valleys, and reservoirs. Several pyroclastic flows left about 0.05 cubic mile of deposits in this area. About 230 square miles were devastated by the eruption." (The Eruption, NGDC, p.4).]

To affect the worldwide temperature, how much dust and ash would have to be added to the upper atmosphere?

[With Mt. St. Helen's I did find out that in addition to the ash cloud that stayed near the ground, millions of tons of fine ash were thrown high into the air and carried hundreds and thousands of miles downwind. These clouds, easily seen in satellite images, dropped several inches of ash over many communities and agricultural areas, ruining machines and crops. I would suggest we look at impacts on the state of Washington rather than worldwide consequences.]

What is the elevation of Mt. Pinatubo compared to Mt. Rainier?

[Mt. Pinatubo is on the island of Luzon in the Philippines and rises to an elevation of 4,875 feet (Mt. Rainier's elevation is 14,410 feet).]

You will notice that the questions above have answers posted with them. When working with your team, you and your teammates are supposed to divide the responsibility for doing research to find the answers to the questions generated in Step 4. Dividing the responsibility for answering these questions is Step 5 of the PBL Model, where you plan your investigation and determine what needs to be done. Doing PBL Steps 4 and 5 are intended to help you and your team to better understand the event as it relates to the problem and will aid in the development of a problem statement (Step 6).

Step 6 of the PBL Model is developing a problem statement. A problem statement is a one or two sentence idea that clearly identifies what your team is trying to solve, produce, respond to, test, or find out.

Below is an example of a problem statement that could have evolved from the ESS analyses and list of questions concerning the Volcano Scenario. This is only one of many problem statements that could have been written.

Our task is to assess how a Pinatubo magnitude event at Mt. Rainier would impact the Earth systems within Washington State. Working from the assumption that the cities and towns around Mt. Rainier have emergency evacuation plans in place, the results of our analysis and subsequent recommendations will pay special attention to:
  • Types of volcanoes and the meaning of magnitude
  • Indicators of pending eruptions and warning timeline
  • Specific short-term Earth system impacts in Washington State
  • Hazard Zone sequence information to include potential amounts, direction and duration of ash fall; pyroclastic flow; lahars; and gases.

At this point you are done reading the team assignment sample responses. Next week—Week 4—you will begin the first of four, three week cycles. During these cycles you will work individually and in teams to complete the steps in the PBL Model.

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