Mount St. Helens is an active stratovolcano located in Skamania County, Washington, in the Pacific Northwest region of the United States. It lies 52 miles (83 km) northeast of Portland, Oregon, and 98 miles (158 km) south of Seattle. Mount St. Helens takes its English name from that of the British diplomat Alleyne Fitzherbert, 1st Baron St Helens, a friend of explorer George Vancouver who surveyed the area in the late 18th century. The volcano is part of the Cascade Volcanic Arc, a segment of the Pacific Ring of Fire.
The Cascade Range or Cascades is a major mountain range of western North America, extending from southern British Columbia through Washington and Oregon to Northern California. It includes both non-volcanic mountains, such as many of those in the North Cascades, and the notable volcanoes known as the High Cascades. The small part of the range in British Columbia is referred to as the Canadian Cascades or, locally, as the Cascade Mountains. The highest peak in the range is Mount Rainier in Washington at 14,411 feet (4,392 m).
Pierce County is a county in the U.S. state of Washington. As of the 2020 census, the population was 921,130, up from 795,225 in 2010, making it the second-most populous county in Washington, behind King County, and the 59th-most populous in the United States. The county seat and largest city is Tacoma. Formed out of Thurston County on December 22, 1852, by the legislature of Oregon Territory, it was named for U.S. President Franklin Pierce. Pierce County is in the Seattle metropolitan area.
Orting is a city in Pierce County, Washington, United States. The population was 9,041 at the 2020 census. It is located between the Puyallup and Carbon rivers in central Pierce County, approximately 30 miles (48 km) northwest of Mount Rainier.
Puyallup is a city in Pierce County, Washington, United States. It is on the Puyallup River about 10 miles (16 km) southeast of Tacoma and 35 miles (56 km) south of Seattle. The city had a population of 42,973 at the 2020 census.
Sumner is a city in northern Pierce County, Washington, United States. The population was 10,621 at the 2020 census. Nearby cities include Puyallup to the west, Auburn to the north, and Bonney Lake to the east.
A lahar is a violent type of mudflow or debris flow composed of a slurry of pyroclastic material, rocky debris and water. The material flows down from a volcano, typically along a river valley.
Nevado del Ruiz, also known as La Mesa de Herveo is a volcano on the border of the departments of Caldas and Tolima in Colombia, being the highest point of both. It is located about 130 km (81 mi) west of the capital city Bogotá. It is a stratovolcano composed of many layers of lava alternating with hardened volcanic ash and other pyroclastic rocks. Volcanic activity at Nevado del Ruiz began about two million years ago, during the Early Pleistocene or Late Pliocene, with three major eruptive periods. The current volcanic cone formed during the present eruptive period, which began 150,000 years ago.
Glacier Peak or Dakobed is the most isolated of the five major stratovolcanoes of the Cascade Volcanic Arc in the U.S state of Washington. Located in the Glacier Peak Wilderness in Mount Baker–Snoqualmie National Forest, the volcano is visible from the west in Seattle, and from the north in the higher areas of eastern suburbs of Vancouver such as Coquitlam, New Westminster and Port Coquitlam. The volcano is the fourth tallest peak in Washington state, and not as much is known about it compared to other volcanoes in the area. Local Native Americans have recognized Glacier Peak and other Washington volcanoes in their histories and stories. When American explorers reached the region, they learned basic information about surrounding landforms, but did not initially understand that Glacier Peak was a volcano. Positioned in Snohomish County, the volcano is only 70 miles (110 km) northeast of downtown Seattle. From locations in northern Seattle and northward, Glacier Peak is closer than the more famous Mount Rainier (Tahoma), but as Glacier Peak is set farther into the Cascades and almost 4,000 feet (1,200 m) shorter, it is much less noticeable than Mount Rainier.
The Puyallup River is a river in the U.S. state of Washington. About 45 miles (72 km) long, it is formed by glaciers on the west side of Mount Rainier. It flows generally northwest, emptying into Commencement Bay, part of Puget Sound. The river and its tributaries drain an area of about 948 square miles (2,460 km2) in Pierce County and southern King County.
The Armero tragedy occurred following the eruption of the Nevado del Ruiz stratovolcano in Tolima, Colombia, on November 13, 1985. The volcano's eruption after 69 years of dormancy caught nearby towns unprepared, even though volcanological organizations had warned the government to evacuate the area after they detected volcanic activity two months earlier.
Tehaleh, formerly known as Cascadia, is a master-planned unincorporated community to the south of Bonney Lake in Pierce County, Washington, United States. Construction began in 2005 with an estimated timeline for completion of 20 years. The town was designed by Patrick Kuo, who had purchased the land in 1991. Included in the original plan for Cascadia were 6,500 homes, a commercial district, an industrial park, schools, and recreational parkland for residents to enjoy. Construction halted in 2008, prior to the construction of any homes or commercial properties. After foreclosure proceedings in 2010, Homestreet Bank repossessed much of Kuo's land, intending to find another developer.
The Cascade Volcanoes are a number of volcanoes in a volcanic arc in western North America, extending from southwestern British Columbia through Washington and Oregon to Northern California, a distance of well over 700 miles (1,100 km). The arc formed due to subduction along the Cascadia subduction zone. Although taking its name from the Cascade Range, this term is a geologic grouping rather than a geographic one, and the Cascade Volcanoes extend north into the Coast Mountains, past the Fraser River which is the northward limit of the Cascade Range proper.
Mount Rainier, also known as Tahoma, is a large active stratovolcano in the Cascade Range of the Pacific Northwest in the United States. The mountain is located in Mount Rainier National Park about 59 miles (95 km) south-southeast of Seattle. With an officially recognized summit elevation of 14,410 ft (4,392 m) at the Columbia Crest, it is the highest mountain in the U.S. state of Washington, the most topographically prominent mountain in the contiguous United States, and the tallest in the Cascade Volcanic Arc.
The Mount Rainier Volcano Lahar Warning System consists of two separate components, operating in tandem: Acoustic Flow Monitors (AFM) and the All Hazard Alert Broadcast (AHAB) sirens. The AFM system was developed by the United States Geological Survey (USGS) in 1998 and is now maintained by Pierce County Emergency Management. The purpose of the warning system is to assist in the evacuation of residents in the river valleys around Mount Rainier, a volcano in Washington, in the event of a lahar. Pierce County works in partnership with the USGS, the Pacific Northwest Seismic Network (PNSN), Washington Military Department's Emergency Management Division, and South Sound 9-1-1 to monitor and operate the system.
Alderton is a census-designated place (CDP) in Pierce County, Washington, United States. The population was 2,893 at the 2010 census. The community is located in the Puyallup River Valley between the cities of Sumner and Orting.
Lake Kapowsin is a lake in Pierce County, Washington, about halfway between Tacoma on Puget Sound, and Mount Rainier in the Cascade Mountains. The lake is 2.5 miles (4.0 km) long and 0.15–0.5 miles (0.24–0.80 km) wide, lying in a channel formed by meltwater from the Puget lobe of the Vashon glacier during the Pleistocene glaciation. A small island, Jaybird Island, lies in the northern half of the lake. As indicated by a drowned forest in the lake and other evidence, the Puyallup River was inundated about 550 years ago by a lahar from Mount Rainier called the Electron Mudflow. The mudflow partially filled the channel and blocked Ohop Creek's outlet, forming present-day Lake Kapowsin.
The Osceola Mudflow, also known as the Osceola Lahar, was a debris flow and lahar in the U.S. state of Washington that descended from the summit and northeast slope of Mount Rainier, a volcano in the Cascade Range during a period of eruptions about 5,600 years ago. It traveled down the west and main forks of the White River, passed the location of present-day Enumclaw then reached Puget Sound in several areas, including near the present day sites of Tacoma and Auburn.
The Electron Lahar, also known as the Electron Mudflow, was a lahar in the U.S. state of Washington that descended from the summit and sunset amphitheater on Mount Rainier about 500 years ago. It was named after the unincorporated community of Electron.
