Volcanoes LAB

10 km

Contour interval = 1000 feet

100010

00

Rivers & streams

Contour line

Major metropolitan area (city)

Suburbs (growing)

Logging forestN

2000

1

2

3

5

4

2 Locations of pictures

10 km

Contour interval = 1000 feet

100010

00

2000

N

Major roads

Smaller roads Small town or village

4

5

3

2

1

Numbers indicate locations of volcanic deposits (see following slides).

Volcano Scenario 6 – History of Eruptions

• Large eruptions involving multiple hazards occurred about 13,000 years ago and about 6,000 years ago. For the past 2,900 years, only small eruptions have happened. The small eruptions involved the growth and collapse of lava domes with small lahars and pyroclastic flows at about 2900 and 2000 years ago, and again between 850-1200 years ago (multiple events).

• In the most recent events, lahars and pyroclastic flows have traveled up to 15 km from the vent, but most are smaller. Ash from an eruption about 6,000 years ago can be found 100’s of kilometers away, and had a total volume beween 10-100 km3. Most ash deposits are more localized, closer to the volcano.

View of volcano

Volcanic deposits (3 different deposits). Middle layer is about 2 feet thick. Location 1 on map.

Volcanic deposit. Location 2 on map.

Volcanic deposit along road at Location 4 on map. hammer handle in center is about 40 cm long

(about 16 inches)

Volcanic deposit. Location 3 on map. Largest block is about 1 foot across.

Volcanic deposit – location 3.

Note cracks radiating from the center of this block. This indicates a significant difference in temperature between the block (hot) and surrounding matrix (cold).

Volcanic deposit along road at Location 5. Close-up of this rock (below right).

Young volcano deposit near summit. Note small glaciers at summit.

Photo source: U.S. Geological Survey