5
Geology 112 Spring 2014 San Jose State University Department of Geology Mt. Rainier and Its Potential Risks Mt. Rainier, a massive stratovolcano currently in rest, is the highest peak in the Cascade Volcanic Arc. It is located 54 miles (87 km) southeast of Seattle in the state of Washington, United States. Mt Rainier is considered one of the most dangerous volcanos in the world, with a height of 14,441 feet (4,392 meter above sea level). The associated tectonic setting of the Cascade Range is a subduction zone, formed along the convergent boundary, where oceanic crust Juan de Fuca Plate is subducted under the lesser dense North America Plate. Mt. Saint Helen, a sister of Mt Rainier, is about 15 miles away from Mt. Rainier. It has erupted in 1980, which cause a destruction landslide traveled about 14 miles west down the North Fork Toutle River. The hazard of Mt. Rainier is similar to what happened with Mt. St Helens, includes landslide, lahar, ash flow, ash fall which can destroy Cowlitz Valley, Nisqually Valley, Puyallup Valley ( Puyallup), White River Valley (Enumclaw, Auburn, Kent, Seattle). Because we don’t have much record of the last several eruption of Mt. Rainier, the 1

Mt Rainier Essay

  • Upload
    bao-lam

  • View
    81

  • Download
    3

Embed Size (px)

DESCRIPTION

Mt. Rainier Risk and Mitigation method

Citation preview

Geology 112Spring 2014San Jose State UniversityDepartment of GeologyMt. Rainier and Its Potential RisksMt. Rainier, a massive stratovolcano currently in rest, is the highest peak in the Cascade Volcanic Arc. It is located 54 miles (87 km) southeast of Seattle in the state of Washington, United States. Mt Rainier is considered one of the most dangerous volcanos in the world, with a height of 14,441 feet (4,392 meter above sea level). The associated tectonic setting of the Cascade Range is a subduction zone, formed along the convergent boundary, where oceanic crust Juan de Fuca Plate is subducted under the lesser dense North America Plate. Mt. Saint Helen, a sister of Mt Rainier, is about 15 miles away from Mt. Rainier. It has erupted in 1980, which cause a destruction landslide traveled about 14 miles west down the North Fork Toutle River. The hazard of Mt. Rainier is similar to what happened with Mt. St Helens, includes landslide, lahar, ash flow, ash fall which can destroy Cowlitz Valley, Nisqually Valley, Puyallup Valley ( Puyallup), White River Valley (Enumclaw, Auburn, Kent, Seattle). Because we dont have much record of the last several eruption of Mt. Rainier, the scientists have no idea when it will erupt again. That means a continuous monitoring system must be enforced to have a warning in advance prior to the eruption occurring. In the worst scenario, when the volcano awakes, it will make the ice on top cone melts down and wipes the whole forest on its side. The result of this is the lahar, which is a type of mudflow or debris flow composed of slurry of pyroclastic material, rocky debris, and water. The hazard of lahar sometimes is bigger than the pyroclastic flow because it contains large debris and it can destroy road, bridges and houses on its way. The dangerous area is located near the volcano site such as Cowlitz Valley, Nisqually Valley, Puyallup Valley and White River Valley. Since the slope of Mt. Rainier mostly forms by layers of lava, it is unstable. A massive landslide can happen as it did happen in 1980 at Mt. St. Helens. Landslide can travel hundred miles per hour and kill many people if they dont get the warning soon enough. Ash fall is also a potential hazard of Mt. Rainier. Since there are many cities near the volcanos site, the ash fall can effect directly to the local community. Volcanic ash is rock that has been moldered into sand or dust in micro size by volcanic activity. In very large eruptions, ash escapes along with rocks having the weight and density and forms hailstones. Volcanic ash cools down as it goes farther the volcano. However, it still can affect the respiratory system; damage the vehicles and even jet plane engines, or destroy the local farms. The ash fall can cover several feet near the volcanic site and it takes a long time to clean up. Lava flow is also produced if Mt. Rainier awakes. As mentioned, Mt. Rainier is a stratovolcano so it can cause pyroclastic flow when it erupts. Usually this kind of volcano has high viscosity, high volatiles and large volume so that its destruction cant be impenetrate. When the magma rises, it is compressed and blocked by a layer of rock. The top layer will be broken if the pressure is too high and the blast occurs. At this stage, there will be ash flow and gas escape from the volcano and rises up to thousand miles. The wind also contributes in spreading the gas and ash to a wider area. As the mixture travels, it will combine with the steam and cause acid rain which can destroy metallic objects. Knowing the hazard of Mt. Rainier, scientists have launched many monitoring station around the mountain. Seismic stations around the foot of Mt. Rainier and inside the ground can discover any small change inside the volcano. These stations help the trackers give ahead warning if theres any suspect. Besides, the lahar warning systems operate continuously can find and send report to the volcanic tracking center so that they will know if the eruption causes lahar. These stations are often set hundred miles away from the nearest city to ensure they have enough time to evacuate after the warning were given. The mitigation plan must be prepare and practice carefully before the eruption occurs. The very first issue is the communication between the scientists and the officials. There was lot of disaster caused large casualties because the governors didnt listen to the warning, for example the hurricane Katrina. In one hand, the governor officials obligation is preparing the public shelters and supplies, engaging an evacuation plan and practice regularly. Hospital and medical services must be able to provide emergency support if the explosion happens. In the other hand, the residents must also prepare for any emergency can occur. They must store enough foods and water for several days. If their house is located near the volcano site, they have to evacuate right after receiving the warning. Understanding the evacuation routes can help them run quickly. While going to the shelters, everyone must follow the authorized personnels order to help them and other people can escape safely. 1