Breakdown: Why landslides happen more in the US than anywhere else in the world

Landslides-why they occur & are most common in the US

MEMPHIS, Tenn. (WMC) - Did you know more landslides happen in the United States than anywhere else in the world?

In the U.S., landslides cause about $3.5 billion in damage and kill between 25 and 50 people each year. Landslides can differ in size, from as small as a single boulder to as big as thousands of tons of earth and debris slides.

There are multiple causes for landslides. Natural occurrences like earthquakes, water erosion, waves, volcanoes and even glaciers are responsible. Some areas of the country are more susceptible to landslides due to geology and soil composition. Human activity also contributes to landslides.

The pictures of landslides are fascinating yet devastating to those involved. So what are they exactly?

A landslide is the sliding down of a mass of earth or rock from a mountain or cliff. Erosion by rivers, glaciers or ocean waves makes slopes too steep.

Gravity is the main culprit for landslides, but there are other factors too.

Landslides can be initiated in slopes already on the brink of movement by heavy rainfall, melting snow, changes in water level, stream erosion, changes in ground water, earthquakes, volcanic activity, disturbance by human activities or any combination of these factors, and according to experts, the cause isn’t always identifiable.

Landslides often follow earthquakes, floods, storm surges, hurricanes, wildfires or volcanic activity. They are typically more damaging and deadly than the event that triggered it.

They normally start on steep hills that liquefy and accelerate to speeds that are typically about 10 miles per hour but can exceed 35 miles per hour. There are many ways this can happen that include a wide range of ground movements, such as falling rocks, slope failures, mudflows and debris flows.

Slopes of rock and soil can get weak through saturation by snowmelt or heavy, excessive rains. Earthquakes create stresses that make weak slopes fail because volcanic eruption produce loose ash deposits, heavy rain and debris flows.

Earthquakes and other factors can also induce landslides underwater. These landslides are called submarine landslides. Submarine landslides sometimes cause tsunamis that damage coastal areas.

There are not always signs of an impending landslide, but sometimes there can be a few clues. Some of the signs are windows that jam for the first time or cracks in plaster.

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