Mass Wasting The downslope movement of rock and soil due to gravity

Mass Wasting

The downslope movement of rock and soil due to

gravity

From A Homeowners Policy(Why this is so important)

From A Homeowners Policy(Why this is so important)

What triggers mass wasting?

1. Gravity

2. Water Diminishes particle

cohesion Water adds weight

3. Oversteepening of slopes

Stable slope angle (angle of repose) is different for various materials

4. Removal of anchoring vegetation, such as by fire

5. Ground vibrations from earthquakes

May cause expensive property damage

Can cause liquefaction – water saturated surface materials behave as fluid-like masses that flow

Landslide triggered by 1994 North earthquake in S. California

Forms of mass wasting

1. Slump Movement along a

curved surface

2. Rockfall Blocks of

bedrock slide down a slope

Generally very fast and destructive

Rockfall Debris

Rockfall in action

3. Mudflow Consists of soil with

a large amount of water

Dry areas after heavy rain

A lahar from the 1980 Mt. St. Helens eruption

Box 09.01.f2a

Box 09.01.f2b

4. Landslide Rock and soil

suddenly fall Steep slopes

Landslide photo

5. Creep Very slow

movement downhill

Creeping Headstones

6. Solifluction Slow, downslope flow of water

saturated soil over frozen layers

Curved trees Stuck windows Stuck doors Leaning walls Plaster cracks Foundation cracks Damaged chimneys Leaning poles Scarps Toes Seeps Pavement damage

Curved trees Stuck windows Stuck doors Leaning walls Plaster cracks Foundation cracks Damaged chimneys Leaning poles Scarps Toes Seeps Pavement damage

Recognizing Problem AreasRecognizing Problem Areas

Be suspicious! Check target and adjacent properties Some problems can be fixed Fixes are temporary and expensive Get expert advice Soil Conservation Service /

Geological Survey

Be suspicious! Check target and adjacent properties Some problems can be fixed Fixes are temporary and expensive Get expert advice Soil Conservation Service /

Geological Survey

Before buying on a hillside:Before buying on a hillside:

Get expert advice Your efforts will probably give temporary relief

Support the base Anchor through slip plane Lower water table Runoff control Plant vegetation Excavate slide mass

Get expert advice Your efforts will probably give temporary relief

Support the base Anchor through slip plane Lower water table Runoff control Plant vegetation Excavate slide mass

Landslide StabilizationLandslide Stabilization

Landslide Diagnosis "A"Landslide Diagnosis "A"

Landslide Diagnosis "B"Landslide Diagnosis "B"

Landslide Diagnosis "C"Landslide Diagnosis "C"

Landslide Diagnosis "D"Landslide Diagnosis "D"