Washington State Geography

Natural Forces That Affect Its Inhabitants

Much of the following information may be found at http://emd.wa.gov

Earthquake

• An earthquake is the sudden release of stored energy; most earthquakes occur along a fracture within the earth, called a fault. The shaking caused by this sudden shift is often very small, but occasionally large earthquakes produce very strong ground shaking. It is this strong shaking and its consequences – ground failure, landslides, liquefaction – that damages buildings and structures and upsets the regional economy.

Earthquake

• Washington, especially the Puget Sound basin, has a history of frequent earthquakes. More than 1,000 earthquakes occur in the state each year. A dozen or more are strong enough that people feel ground shaking; occasionally, earthquakes cause damage.

Earthquake• Large earthquakes in 1946 (magnitude 5.8), 1949

(magnitude 7.1) and 1965 (magnitude 6.5) killed 15 people and caused more than $200 million (1984 dollars) in damage throughout several counties. The state experienced at least 20 damaging events in the last 125 years.

Earthquake

• The Nisqually earthquake on February 28, 2001,

was a deep, magnitude 6.8 earthquake 10 miles northeast of Olympia. One person died of a heart attack, more than 700 people were injured, and various estimates place damage at between $1 billion and $4 billion; exact figures are not available , as insurance claims information is not available.

Volcano

• Washington’s volcanoes will erupt again, but none show signs of imminent activity. Because people are moving into areas near these mountains at a rapid pace, the state’s volcanoes are among the most dangerous in the United States.

Volcano

• Mount Baker in Whatcom County erupted in the mid-1800s for the first time in several thousand years. Activity at steam vents in Sherman Crater, near the volcano's summit, increased in 1975 and is still vigorous, but there is no evidence that an eruption is imminent.

Volcano

• Glacier Peak in Snohomish County has erupted at least six times in the past 4,000 years. An especially powerful series of eruptions about 13,000 years ago deposited volcanic ash at least as far away as Wyoming.

VolcanoVolcano

• Mount Rainier in Pierce County is one of the most hazardous volcanoes in the United States. It has produced at least four eruptions and numerous lahars in the past 4,000 years. It is capped by more glacier ice than the rest of the Cascades volcanoes combined, and Rainier's steep slopes are under constant attack from hot, acidic volcanic gases and water. These factors make this volcano especially prone to landslides and lahars. More than 150,000 people live on former lahars in river valleys below the volcano.

Volcano

• Mount St. Helens in Skamania County is the most frequently active volcano in the Cascades. During the past 4,000 years, it has produced many lahars and a wide variety of eruptive activity, from relatively quiet outflows of lava to explosive eruptions much larger than that of May 18, 1980.

Volcano• Mount Adams in Yakima County has produced

few eruptions during the past several thousand years. This volcano's most recent activity was a series of small eruptions about 1,000 years ago.

Severe Storms

• All areas of Washington State are vulnerable to severe weather. A severe storm is an atmospheric disturbance that results in one or more of the following phenomena: strong winds and large hail, thunderstorms, tornados, rain, snow, or other mixed precipitation. Typically, major impacts from a severe storm are to transportation and loss of utilities. Most storms move into Washington from the Pacific Ocean.

Severe Storm• High winds – Storms with sustained

winds of 40 mph or gusts of 58 mph or greater, not caused by thunderstorms, expected to last for an hour or more.

Severe Storm

• Severe Thunderstorm – Storms that produce winds of 58 mph or greater or three-quarter inch or larger hail.

Severe Storm• Tornado – A storm with a violently rotating

column of air that contacts the ground; tornados usually develop from severe thunderstorms. Tornados can produce winds of 100 to 300 mph.

Not a picture from Washington State

Severe Storm

• Winter storm – A storm with significant snowfall, ice, and/or freezing rain; the quantity of precipitation varies by elevation. Heavy snowfall is 4 inches or more in a 12-hour period, or 6 or more inches in a 24-hour period in non-mountainous areas; and 12 inches or more in a 12-hour period or 18 inches or more in a 24- hour period in mountainous areas.

Severe Storm

• Blizzard – A storm with considerable falling and/or blowing snow combined with sustained winds or frequent gusts of 35 mph or greater that frequently reduces visibility to less than one-quarter mile. Blizzards typically are confined to the Columbia River Gorge and Northwest Washington near the Fraser River Valley of British Columbia.

Severe Storm

• Dust storm – A storm of dust and debris blown by wind gusts of at least 35 mph, or caused by a downburst from a dry thunderstorm, that reduces visibility to less than one-quarter mile.

Not an image from Washington State

Severe Storm

• Coastal flooding – Flooding in coastal areas caused by storm surge, astronomical high tides, or a combination of them.

Avalanche

• An avalanche occurs when a layer of snow loses its grip on a slope and slides downhill.

Avalanche

• Avalanches have killed more than 190 people in the past century in Washington State, exceeding deaths from any other natural hazard. One of the nation’s worst avalanche disasters occurred in 1910 when massive avalanches hit two trains stopped on the west side of Stevens Pass; 96 people were killed.

Avalanche• Avalanches kill one to two

people, on average, every year in Washington, although many more are involved in avalanche accidents that do not result in fatalities.

• Since 1985, avalanches have killed 23 people. Most current avalanche victims are participating in recreational activities in the backcountry where there is no avalanche control.

Avalanche

Only one-tenth of one percent of avalanche fatalities occurs on open runs at ski areas or on highways.

Flood

• Floods cause loss of life and damage to structures, crops, land, flood control structures, roads, and utilities. Floods also cause erosion and landslides, and can transport debris and toxic products that cause secondary damage. Flood damage in Washington State exceeds damage by all other natural hazards.

Flood

• There have been 28 Presidential Major Disaster Declarations for floods in Washington State from 1956 through October 2003. Every county has received a Presidential Disaster Declaration for flooding since 1970. While not every flood creates enough damage to merit such a declaration, most are severe enough to warrant intervention by local, state or federal authorities.

Flood• Since 1980, federal, state

and local governments have invested more than $522 million to repair public facilities, help individuals recover from flood disasters, and pay for measures to prevent future flood damage. This is nearly 40 percent of the more than $1.37 billion amount spent on disaster relief and hazard mitigation during this time

Landslide• Landslide is the movement of rock, soil and debris

down a hillside or slope. Landslides take lives, destroy homes, businesses, and public buildings, interrupt transportation, undermine bridges, derail train cars, cover marine habitat, and damage utilities.

LandslideGround failures that result in landslides occur when gravity overcomes the

strength of a slope. While gravity is the primary reason for a landslide, there can be other contributing factors, including:

• Saturation, by snowmelt or heavy rains, that weaken rock or soils on slopes. • Erosion by rivers, glaciers, or ocean waves that create over-steepened

slopes. • Topography of a slope – its shape, size, degree of slope and drainage. • Stress from earthquakes magnitude 4.0 and greater can cause weak slopes

to fail. • Volcanic eruptions that produce loose ash deposits and debris flows. • Excess weight, from accumulation of rain or snow, from stockpiling of rock

or ore, from waste piles, or from manmade structures, may stress weak slopes to failure.

• Human action, such as construction, logging or road building that disturbs soils and slopes.

Wildfire• Wildland fires are fires caused by nature or

humans that result in the uncontrolled destruction of forests, brush, field crops, grasslands, and real and personal property.

Wildfire

• The wildland fire season in Washington usually begins in early July and typically culminates in late September with a moisture event; however, wildland fires have occurred in every month of the year. Drought, snow pack, and local weather conditions can expand the length of the fire season. The early and late shoulders of the fire season usually are associated with human-caused fires. Lightning generally is the cause of most fires in the peak fire period of July, August and early September.

Sources

• http://www.wa.nrcs.usda.gov/news/flood.html

• http://flickr.com/photos/wsdot

• http://wsdot.wa.gov/traffic

• http://emd.wa.gov

• www.ecy.wa.gov

• www.soundseismic.com