Scientists are concerned about Mount Rainier

Within the last week, there have been some news articles featured on major news networks as to the possibility of a potential eruption of Mount Rainier. With an elevation of 14,411 feet and located about 60 miles southeast of the Seattle/Tacoma region, it’s not only the tallest mountain in Washington but also the highest in the Cascade Volcanic Arc in western North America.

Mount Rainier is an active volcano and volcanologists are very concerned that a future eruption would pose a massive threat to communities, especially around Puget Sound. A volcanism project from the Smithsonian Institution estimates that the last major eruption occurred at 1450 AD/CE. However, the most recent activity was between 1820 and 1854, but there were eyewitness reports that indicated there was some kind of eruption as late as 1894.

Most of the volcanoes in the world are classified as either a stratovolcano or a shield volcano. Explosive eruptions are from stratovolcanoes, such as Mount Rainier, which usually have a cone-shaped mountain, compared to more long, gentle slopes of a shield volcano, like the ones on Hawaii’s Big Island. The volcanoes that are highly explosive have very sticky magma that does not flow easily, compared to more fluid types of magma that will travel great distances when there is an eruption. The volcanoes in the western U.S. are more likely to produce strong eruptions due to the sticky lava and gas buildups.

According to a report from the United States Geological Survey, Mount Rainier’s next eruption, may produce volcanic ash, lava flows or pyroclastic flows. A pyroclastic flow from an erupting volcano is a very hot mixture of gas, ash and rock fragments that have a temperature of up to 1,500 degrees Fahrenheit. Depending on the explosion, this type of flow can reach speeds of close to 200 miles per hour.

What separates Mount Rainier from many other volcanoes are the glaciers and snowfields. With approximately 26 glaciers, the mountain is the most heavily glaciated peak across the continental U.S. The major concern with a future eruption is the heat from the explosion would rapidly melt the snow and ice creating a “lahar.” This is an Indonesian word for volcanic mudflows and are far more hazardous and deadly. The USGS says that lahars “look and behave like flowing concrete, and their impact forces destroy most human-made structures.” Based on geological evidence, lahars have reached the Puget Sound region at least every 500 to 1,000 years.

The most destructive lahar in recent history occurred in November 1985. Known as the Armero tragedy, the Nevado del Ruiz volcano exploded in Tolima, Colombia. The volcano was quiet for nearly 70 years and, despite the detection of volcanic activity, caught the towns surrounding the volcano unprepared for the disaster. The eruption sent four large lahars down its slopes and killed more than 20,000 people. Mount Rainier has at least a dozen more glaciers than the Nevado del Ruiz volcano when it erupted in 1985.

Predicting a major volcanic eruption has not quite become a reality, but much progress has been made. Many explosions are often preceded by earthquakes, swelling of the ground, the formation of cracks and the release of gases. There are thermal infrared sensors in satellites to help detect the hot spots. More recently, there is also a system for automatic detection and notification of lahars. An acoustic flow monitor can detect ground vibrations of a lahar, which was developed by the USGS.

The USGS reported back in 2018 that Hawaii’s Kilauea is the most hazardous volcano in the United States. In second place is Mount St. Helens, with Mount Rainier in third place. The chances of an eruption that produces a lahar reaching Puget Sound within 75 years is about 10%.

In terms of our local weather, June’s precipitation is going to end up very close to the 1.93-inch normal. Some locations in the outlying areas will have a wetter-than-normal June thanks to the thunderstorm activity last week. For example, Hayden picked up nearly an inch of rain from that system alone.

June’s high temperatures in Coeur d’Alene did not produce a 90-degree afternoon. However, there was one 90-degree day at the Spokane International Airport on June 22.

The long-range computer models are indicating some 90-degree temperatures and dry weather over the next few weeks. There is a chance of scattered showers or a thunderstorm around the middle of the month. Cliff and I do believe that we’ll have a period of about four to six weeks of very warm to hot weather with below-normal precipitation this summer. By late August and September, precipitation totals are expected to climb to near or above normal levels in our region as we should start to see more of an influence from the cooling of sea-surface temperatures along the Equator.

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Contact Randy Mann at randy@longrangeweather.com.