Resolution_2025 Kittitas County Hazard Mitigation Plan

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2025 Hazard Mitigation Plan Kittitas County, Washington Chapter 4: Hazard Identification and Risk Assessment 182 Volcano Eruption History Glacier Peak Glacier Peak erupts frequently. The eruptions are typically explosive and occasionally voluminous. Most eruptions involve tephra, but many were accompanied by far reaching lahars and dome building. Glacier Peak has erupted multiple times in the last 15,000 years. About 13,000 years ago, a series of large tephra eruptions occurred, accompanied by numerous lahars. One (1) eruption was many times the size of the Mount St. Helens 1980 eruption. Within th e last 5,000 years, the volcano has produced frequent lava dome eruptions and subsequent dome collapses and lahars. The most recent eruption was approximately 300 years ago. Mount Rainier Mount Rainier started erupting about 500,000 years ago with intermittent eruptions and mudflows thereafter, and it still issues steam and gases from fumaroles near the summit crater. Heat from the fumaroles melts the snow and ice at the crater, as well as the summit icecap, forming caves beneath the ice. Mount St. Helens Mount St. Helens was formed from four (4) eruptive stages starting approximately 275,000 years ago, and intermittent eruptions currently occur. The most significant eruption occurred in 1980 after a series of earthquakes, steam explosions, and small eruptions at the summit signaled a new eruptive phase of the volcano. By mid-April 1980, a large bulge of new volcanic material had formed on the north flank of the mountain and moved outward at an average rate of five (5) feet per day. In addition to ash, pyroclastic flows and lahars traveled swiftly across the Pumice Plain and down the North Fork Toutle and Cowlitz Rivers, destroying houses and bridges along the way. Dome building eruptions occurred between 1980 and 1986, and 2004 and 2008. 4.6.8.6. Vulnerability and Impacts According to the 2023 Washington State Enhanced Mitigation Plan, Kittitas County is not at risk of exposure to lahar or lava flow. However, ashfall can travel much further and all of Kittitas County is vulnerable to ashfall from any of the active volcanoes in the region. The following vulnerabilities and impacts will mostly focus on ashfall. Life Safety and Health: The entire Kittitas County population is vulnerable to the hazards of volcanic activity due to its proximity to volcanoes in the Cascade Range. Life safety and health concerns after a volcanic eruption include, but are not limited to, infectious disease, respiratory illness, burns, injuries from falls, and vehicle accidents related to the slippery, hazy conditions caused by ash. Volcanic ash particles can scratch the front of the eyes; and ash particles contain crystalline silica which is a material that causes respiratory diseases such as silicosis. Ash particles can be so fine that they can be inhaled deep into the lungs and with high exposure even healthy individuals can experience respiratory issues. Although volcanic gases tend to quickly get blown away, heavy gases (e.g., carbon dioxide, hydrogen oxide) can remain stagnant in low-lying areas which can irritate the nose, eyes, and throat. At higher elevations, gases can cause rapid breathing, headache, dizziness, swelling, spasm of the throat, and suffocation. Sulfur dioxide can cause breathing problems for both healthy and people with asthma and other respiratory problems.232F 232 Property Damage and Critical Facilities: The closer the property and critical facilities are to the volcano, the higher the exposure to property damage from volcanic related hazards. Impacts to property and critical facilities can range from minor to catastrophic. Volcanic ash can severely disrupt transportation systems (e.g., roads, cars, railways, and aircraft) over extremely large areas for hours to days. Heavy ashfall can affect general road conditions by reducing visibility on highways and railways. Additionally, 232 Centers for Disease Control and Prevention. (2024). Volcanoes and Your Safety. Retrieved from https://www.cdc.gov/volcanoes/about/index.html.