Are there landslides in Washington state?

Are there landslides in Washington state?

Landslides in Washington Landslides are common in Washington state, with many occurring annually in the Puget Sound area, especially along the Sound’s steep shoreline bluffs. Landslide areas are deemed geologically-hazardous, environmentally-critical areas under the state Growth Management Act.

Why does Washington have so many landslides?

Seattle’s geology and climate contribute to landslides The arrangement of glacial deposits and other weak rocks, along with the effects of coastal erosion, define where most landslides occur. Seattle has warm dry summers and cool moist winters.

What can cause land slides?

Landslides are caused by disturbances in the natural stability of a slope. They can accompany heavy rains or follow droughts, earthquakes, or volcanic eruptions. Mudslides develop when water rapidly accumulates in the ground and results in a surge of water-saturated rock, earth, and debris.

What causes landslides in Seattle?

The most frequent triggers of landslides in Seattle are human alteration of the slope, groundwater saturation, or a combination of both. For example, a person may cause a pipe to leak and saturate the ground, triggering a landslide. Landslides that occur under water are called submarine landslides.

What hazards would increase the likelihood of triggering a landslide in Washington?

Human activities – Vegetation removal, surface and underground mining, loading on a slope, excavation of the base of a slope, and leakage from pipes can all trigger landslides.

Why are landslides more common to steep slopes?

A landslide occurs because the force of gravity becomes greater than either friction or the internal strength of the rock, soil, or sediment. Pushing the rock is easier if the surface slopes downhill or is slippery. The same is true for landslides—steeper slopes have less friction, making landslides more common.

What are the human activities that cause landslides?

Human activities can increase landslide risks. They include clear-cutting, mining and quarrying, bad agricultural practices, and construction activities.

Where was the mudslide in Washington state?

Oso
On March 22, 2014, a deadly mudslide devastated the Washington state community of Oso — 60 miles north of Seattle — with up to 70 feet of mud, swallowing part of the Stillaguamish River and a mile-long stretch of state highway 530. Eyewitnesses say a towering wall of mud roared loudly as it raced through the valley.

What are some of the key factors that contributed to the Oso landslide?

The landslide’s high mobility was likely due to several contributing factors, including the soil’s initial porosity and water content from rainfall in the months prior.