Mass-Wasting

Movement of Large Amounts of Material Downhill under Gravity

Types of Mass Wasting

• Slow vs. Fast• Wet vs. Dry• Cohesive vs. Fragmented

Types of Mass Wasting

• Creep• Slow Landslide• Earthflow, Mudflow, Debris Flow• Avalanche• Rockfall• Slump• Complex Landslide

Factors in Mass Wasting

• Climate• Moisture• Steep Slopes• Weak Rocks• Existing Failure Surfaces

Soil Creep

Soil Creep

Soil Creep

Soil Creep, California

Creep, North Carolina

Colluvium, San Bernardino Mountains, California

Mystery or Soil Creep?

Four Years’ Mass-Wasting, Bosnia

Four Years’ Mass-Wasting, Bosnia

• 100*40/2 cm2 = 2000 cm2 (4 years)

• = 500 cm2 /year• Removed from 1 km

slope per year = 500 cm2 /100,000 cm= 1 cm/200 yr= 5000 cm (50 m)/m.y. = 50m /m.y.

• A 1-m (100 cm) soil mantle yields 500 cm2 /year, so movement = 500 cm2 /year/100 cm= 5 cm/year

Debris Flow, Utah

Landslide, Wyoming

Geological Disneyland, Utah

Landslide, Utah

Landslide, Wyoming

Landslide and Slope Control, Wyoming

Landslide, Wyoming

Bridge of the Gods, Washington

Bridge of the Gods, Washington

Gros Ventre Slide, Wyoming, 1925

Slide Lake, Wyoming

Gros Ventre Slide, Wyoming

Landslide, Pakistan, January 4,

2010

Landslide, Pakistan, January 4,

2010

Urban Planning, San Diego

Martian Landslide

Active Landslide on Mars

Active Landslide on Mars

Rockfalls, Yosemite, California

Rockfalls, Yosemite, California

Block Slide, Yosemite

Rockslide, Yosemite

Slumps? Baird Creek

Avalanche Chute, Colorado

Landslide, Mount Saint Helens

Aberfan, Wales

• October 21, 1966, a large waste pile from coal mining collapsed

• Village school was in the path of the slide• 144 people killed, 116 of them children• Weathering of coal mine waste liberates

sulfuric acid and weakens waste piles• Seepage beneath pile contributed

Coal Tip, England

Aberfan Slide

Inquiry Board, 1967

• the Aberfan Disaster is a terrifying tale of bungling ineptitude by many men charged with tasks for which they were totally unfitted, of failure to heed clear warnings, and of total lack of direction from above. Not villains but decent men, led astray by foolishness or by ignorance or by both in combination, are responsible for what happened at Aberfan.

Sherman Glacier, Alaska, March 27, 1964

Sherman Glacier, Alaska,

March 27, 1964

Blackhawk Landslide, California

Saidmareh Landslide,

Iran

Landslide on Iapetus

Viaont, Italy, October 9, 1963

1800 people died.

Yungay, Peru, May 31, 1970

Yungay, Peru, May 31, 1970

Lituya Bay, Alaska, July 9, 1958

Lituya Bay, Before and

After

The Scour Line

The Highest Wave Ever Recorded

Dealing With Mass-Wasting• Proper Land Use – Stay out of Danger• Take warnings seriously• Structural Control– Retaining Structures– Drainage– Terraces

• Warning System• Accept the Risk and Responsibility• Abolish Insurance ?