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Landslides & Mudslides

Landslides and mudslides are masses of rock, earth, or debris moving down a slope. These slides may damage homes, roadways, or other developments in their path. They may be small or large, and may move slowly or very fast.

There are many possible causes of mudslides. Heavy storms may saturate the soil and slopes may slump as a result. The shaking of earthquakes may cause rocks or other material to fall. Wildfires eliminate vegetation that otherwise holds soils in place. Human developments may create unstable slopes that eventually slide. A combination of these factors may increase the likelihood of a landslide.

Debris and mud flows (mudslides) are rivers of rock, earth, and other material saturated with water. Heavy rainfall or rapid snowmelt may cause water to rapidly accumulate in the ground, creating a flowing river of mud. They can flow at high speeds, striking with little or no warning, and can travel several miles from their source, growing in size as they pick up trees, boulders, and other materials.

Learn to recognize warning signs: (Be particularly attentive to signs of slope instability during or after heavy storms or earthquakes, and up to a year after a wildfire.)

  • Changes in landscape, storm water drainage patterns, land movement, small slides, or progressively leaning trees.
  • Doors and windows that stick or jam for the first time
  • New cracks appearing in plaster, tile, brick, or foundations
  • Outside walls, walks, or stairs begin pulling away from the building.
  • Slowly developing, widening cracks appear on the ground or on paved areas, such as streets or driveways.
  • Water breaks through the ground surface at new locations.
  • A faint rumbling sound that increases in volume is noticeable as a mudslide nears.
  • Unusual sounds, such as trees cracking or boulders knocking together, might indicate moving debris.
  • Collapsed pavement, mud, fallen rocks and other indications of possible debris flow can be seen when driving.

For more information on landslides/mudslides visit the American Red Cross website.