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How Landslides Work


People and Landslides
Clear cuts in Prince of Wales Forest, Alaska
Clear cuts in Prince of Wales Forest, Alaska
Chip Porter/Getty Images

Humans make landslides more likely through activities like deforestation, overgrazing, mining and road-building. Remember when we explained that vegetation acts like glue, holding the soil in place? These activities rob that glue from the land, increasing the probability for a landslide. For example, landslides are much more likely to occur in mountainous areas that have been clear-cut for roads. You've probably seen signs warning of rock falls if you've ever driven through the mountains. The drop-offs with loosened soil you see on both sides of the road require much less water to set off a landslide than natural drop-offs.

Although landslides cannot be avoided entirely, people can do several things to discourage them. Drainage pipes installed into slopes can carry away excess water, and impermeable membranes like plastic sheeting can prevent water from building up and dislodging the soil. In addition, setting up retaining walls at intervals will catch loose debris and keep it in place, while removing excess mass from the top of a slope could prevent the bottom from giving way. Reforestation is a good deterrent to landslides as well. When an area is clear-cut for harvesting timber, road-building or mining operations, restoring it to its natural condition stabilizes the land.

Plant roots help hold the soil in place.
Plant roots help hold the soil in place.
Gary Vestal/Getty Images

Perhaps the most important thing people can do to avoid the dangers of landslides is to avoid building in hazardous zones. Ideally, buildings shouldn't be placed on steep slopes or in drainage areas. But if people do build in areas like these that are susceptible to landslides, they should use protective measures. For instance, construction sites should use barriers to mitigate runoff and erosion.

If you find yourself in an area where landslides are likely, be ready with an emergency evacuation plan if there is any danger. Be aware of any sudden rises or falls in water flow and listen for sounds that may signal moving debris or falling rocks. If you suspect landslide activity, you should evacuate immediately if it is safe to do so. Remember to be especially vigilant when driving, as roadside embankments are also hazardous.

While you certainly wouldn't want to be caught in the path of a landslide, it is exciting to view their awesome strength and force on video. Don't miss the close-up footage of landslides in action posted on the following page, as well as the related HowStuffWorks articles and other interesting Web sites.