Debris Avalanches & Mt Rainier

Question 1

Debris Avalanche

Answer 1

Large mass of rock and soil that fall, slide, flow very rapidly due to collapse of an unstable slope.

Disintegrates into fragments during movement.

Question 2

Types of Debris Avalanches

Answer 2

1. Cold Debris Avalanche (unstable slope; hydrothermal alteration (alteration of rock with hot water); oversteepening)
2. Hot Debris Avalanche (result from volcanic activity; volcanic earthquakes; slope instability from magma injection)

Question 3

What Type of Debris Avalanche is Mt. Rainier

Answer 3

Cold Debris Avalanche

Question 4

History of Rainier’s Cold Debris Avalanche

Answer 4

1. Transformed into Lahar (deposits track back to mudflow)
2. Formed horse-shoe shaped crater
3. Rebuilt current Cone (with landslide scar) 1000 and 2300 years ago.
4. Small eruption due to depressurization.

Question 5

Mt. Rainier Debris Avalanche Characteristics

Answer 5

Abundant Water and Heat which results in unstable flank; Conductive to mudflow (melt ice + mix of sediment pyroclastic flows)

Question 6

Debris Avalanche Deposits & Examples

Answer 6

Large composition of debris Avalanche blocks that preserve structure of source.

Horseshoe Crater in South Region Mt. Rainier; Hummocky Topography (larger blocks; bumpy land)