Learning target: I can turn vague goals into precise criteria and constraints, evaluate competing monitoring plans, and design a volcano monitoring network and alert rule that uses precursor data to protect a town.
Silver Basin, the town of Juniper and every cost on this sheet are invented for this challenge; the costs are simulated, not real prices. Work with a partner, but each of you writes your own answers. Read the whole problem first. Then define the problem precisely (Part A), judge two plans the county has already received (Part B), design your own network on the map grid (Part C), and write the rule the observatory will use to raise the alert (Part D).
You will need: This worksheet, Pencil, Calculator, Colored pencils for marking the grid (optional)
Silver Basin is a caldera, a huge bowl-shaped hollow about 15 km across that was left behind when a giant eruption emptied the magma chamber beneath it long ago. The ski town of Juniper, home to 2,500 people and up to 10,000 visitors on winter weekends, sits on the south rim. Two years ago, swarms of small earthquakes began, the center of the basin started rising about 2 cm per year, and two hot-spring vents began giving off more carbon dioxide. The volcano observatory has set the alert level at Advisory. The basin has only one old seismometer, in town. The county has $300,000 to build and run a monitoring network for the next 5 years.
| Measurement | Current value |
|---|---|
| Small earthquakes per week | about 10, at 3 to 6 km deep |
| Uplift at the basin center | about 2 cm per year |
| Carbon dioxide at each vent | about 50 tonnes per day |
| Seismometers working | 1 (in Juniper) |
| Row | 1 | 2 | 3 | 4 | 5 |
|---|---|---|---|---|---|
| A (north rim) | Forest | North rim (no road in winter) | North rim (no road in winter) | Wilderness | Wilderness |
| B | West rim road | Basin floor | Vent 1 (hot springs) | Basin floor | Wilderness |
| C | West rim road | Lake | Uplift center | Basin floor | East rim road |
| D | Basin floor | Lake | Basin floor | Vent 2 (hot springs) | East rim road |
| E (south rim) | Ranch | Highway | Juniper (old seismometer) | Ski area | Highway |
| Instrument | What it does | Cost to install | Upkeep per year |
|---|---|---|---|
| Seismometer station | Records small earthquakes. Four or more stations around an area are needed to locate quakes and find their depth. | $20,000 | $2,000 |
| GPS station | Measures ground rising, sinking or shifting to within a few millimeters, all year. | $15,000 | $1,000 |
| Gas station | Measures carbon dioxide and sulfur dioxide at one vent. | $35,000 | $5,000 |
| Satellite radar processing | Maps uplift across the whole basin every 12 days, but gives poor results when deep snow covers the ground (December to April). | $0 | $8,000 |
| Webcam | Shows the vents and steam; cannot see underground. | $3,000 | $400 |
| 5-year total cost (install + 5 × upkeep) |
|---|
| Seismometer station |
| GPS station |
| Gas station |
| Satellite radar processing |
| Webcam |
Plan X ('Listen hard'): 8 new seismometers spread around and across the basin (one of them on the north rim at A3), 2 webcams and satellite radar. Total: $295,000. Plan Y ('Watch the ground and gas'): gas stations at both vents, 4 GPS stations, 2 new seismometers at E1 and E5 on the south rim, and satellite radar. Total: $300,000.
| Plan X: meets it? (yes, no or partly) and why | Plan Y: meets it? (yes, no or partly) and why |
|---|---|
| Your criterion 1 | |
| Your criterion 2 | |
| Your criterion 3 | |
| Your criterion 4 | |
| Budget constraint |
| Instrument | Grid cell | 5-year cost |
|---|---|---|
| Item 1 | ||
| Item 2 | ||
| Item 3 | ||
| Item 4 | ||
| Item 5 | ||
| Item 6 | ||
| Item 7 | ||
| Item 8 | ||
| Item 9 | ||
| Total |
| Alert level | What it means |
|---|---|
| Normal | Typical background, non-eruptive state. |
| Advisory | Signs of unrest above the known background level. |
| Watch | Heightened or escalating unrest with increased potential for eruption, timeframe uncertain; or a minor eruption under way. |
| Warning | A hazardous eruption is imminent, under way or suspected. |
A precise criterion can be checked with yes or no. Vague: 'cover the volcano well.' Precise: 'At least 4 working seismometers on at least three different sides of the basin, so a quake anywhere under it can be located.' Ask of each criterion: How many? Where? How often? Which signal? For the budget, add the 5-year cost of each item and any solar kits, and check that the total is $300,000 or less.
In year 3 the county's budget is cut and you must drop $60,000 of upkeep and equipment from your network. Decide what to remove and explain which precursor you will now detect later or less reliably. Then research how the USGS California Volcano Observatory monitors a real caldera, Long Valley near Mammoth Lakes, and compare its instruments with your design.