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Landslides are downslope movement, under gravity, of masses of soil and rock material.
Landslides and debris flows (rapidly moving landslides that typically move long distances) are natural processes, triggered or accelerated by these factors:
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Intense or prolonged rainfall, or rapid snow melt, that cause sharp changes in ground water levels.
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Undercutting of a slope or cliff by erosion or evacuation.
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Shocks or vibrations from earthquakes or construction.
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Vegetation removal by fires, timber harvesting, or land clearing.
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Placing fill (weight) on steep slopes.
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A combination of these factors.
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For more information on landslides see the Oregon Department of Geology web site.
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