Living with Active Cascade Volcanoes

Jason Nilsen

- Volcano/Human relationship

- Identify WA Cascade Volcanoes

- Understand Volcanic Hazards

- Risks and Benefits of living near Volcanoes

Objectives

ANDESITE – A lava rock; predominant lava type in most Cascade stratovolcanoes.

ASH CLOUD – A turbulent cloud of ash culminating in an eruption column or ash plume. BASALT – Dark, fine grained lava rock. The most common of earth’s volcanic rock.

COMPOSITE CONE – AKA Stratovolcano, large volcanic mountain constructed of lava flows and pyroclastic material. Most continental volcanoes are of this type.

GLACIER – Large, dense mass of ice, formed on land by refreezing of snowfall.

LAHAR – A mudflow originating on a volcano; composed of rock fragments/water that travels to lowlands.

Terminology

• A growing number of people (currently ~500 million) live on or near one of the ~1000 volcanoes on Earth that are considered geologically active.

• Eruptions at most of these volcanoes are rare on the scale of a human lifetime, but lessons from past eruptions (historic and prehistoric) must not be forgotten.

• Keys to protecting people and property are:1. Assessment - could it erupt? If so, how violently?2. Monitoring - watching for signs of impending eruption3. Mitigation - how to prepare for and respond to an eruption

Volcano/Human Relationship

The locations of the major Cascade volcanoes is shown on the left, and the number of times each has erupted in the last 4000 years is shown on the right (each small puffing volcano symbol denotes an eruption). The red line on the right marks when detailed historical records began in this area about 200 year ago.

Cascade Volcanoes

• The Cascades are a volcanic mountain chain stretching from northern California to southern British Columbia.

• They are a broad (50-80 mile wide) volcanic platform with ~16 major high (10,000-14,000 ft elevation) volcanic cones.

• All historic (since written historical records began in the area) volcanic eruptions in the lower 48 states have been Cascade volcanoes. Baker, Rainier, and St. Helens have been the most active volcanoes in historic times.

1. Mt. Baker, WA – One of the most active Cascade peaks, with many eruptions in the past 10 yrs, possibly as recently as the 1800s.

WA Cascade Volcanoes

3. Glacier Peak, WA - There is no record of recent activity except a possible ashfall in the early 1800s, although hot springs and warm ground occur around Glacier Peak.

4. Mt. Rainier, WA - The highest and one of the largest volcanoes in the Cascades. One of the most dangerous, as parts of Seattle-Tacoma and suburbs sit on deposits from eruptions and collapses of Mt. Rainier. Large lahars occurred at least 3 times in the past 6000 yrs (one as recently as 530 yrs ago) and the extensive hydrothermal alteration at Rainier makes it prone to more mudflows.

5. Mt. Adams, WA - directly east of Mt. St. Helens (the only pair of Cascade volcanoes insuch an alignment), Mt. Adams is the largest Washington Cascade volcano by volume. Most recent eruption aprox 1000 yrs ago.

6. Mt. Saint Helens, WA - The most active Cascade volcano in recent times. Mt. St. Helens is the youngest Cascade volcano, with the oldest deposits dated at only 40k yrs with the main cone built entirely in the past 3k yrs!

WA Cascade Volcanoes

• Eruptions may be violent, destroying lives, infrastructure (homes, cities, roads, railways, power lines, etc.), and natural resources (lakes and rivers, forests, farms and range land).

• Effects may be widespread, especially due to ashfall.

• Airborne ash poses hazards to airplanes.

• Effects may last for years to decades because:

1. loose volcanic deposits are easily eroded and remobilized as mudflows.

2. ecological recovery is slow.

Risks of living near Volcanoes

• Breakdown of volcanic rocks adds mineral nutrients to soil, making volcanic soils some of the most fertile in the world.

• Snow cover on volcanoes provides summertime stream flow and water for drinking, hydroelectric power, and aquatic life.

• Heat from magma inside volcanoes can be a source of geothermal energy that heats buildings and drives generators.

• Volcanoes are sometimes associated with deposits of gold, silver, copper, and other precious metals.

Benefits of living near Volcanoes

I have provided information regarding the human relationship with volcanoes as well as the different Stratovolcanoes in Washington State’s portion of the Cascade Range.

We discussed the risks and benefits of living near these magnificent giants, including types of disasters and transforming the geo-thermal activity for our benefit.

Conclusion

Questions