A hillside shifts sending mud, rocks and trees rumbling down its
Homes and property are buried or swept away. People are left homeless,
injured or even killed.
Worldwide, thousands of people die every year from land and mudslides. In
the United Sates alone, land and mudslides cause an estimated $1 billion in
damage and kill 25 to 50 people every year.
What Causes a Landslide?
First of all, a mudslide is one type of landslide. Steep hills and
mountains are often the site of land and mudslides. Slopes on these hills
and mountains become weakened by many things:
- erosion by rivers, glaciers
or ocean waves
- fires leave slopes bare and
vulnerable to rain
- heavy rain or snowmelt
saturates the ground
- earthquakes weaken the
structure of the slope - volcanic eruptions produce loose ashfall deposits
and debris slopes
- traffic, blasting operations,
machinery and even thunder can vibrate weak slopes
- the weight of snow,
stockpiling of ore, waste piles, and even buildings can put stress on weak
Once a slope is weakened, almost anything can set it off. Rain,
earthquakes, and even blasting are common causes.
If the hillside is dry, dirt and rocks can tumble down the grade. If,
however, the slope is saturated with water, a mudslide occurs. This more
destructive flow can pick up rocks, trees, houses and cars. As the debris
moves into river and stream beds, bridges can become blocked or even
collapse, making a temporary dam that can flood neighboring areas.