Washington volcanoes


Mount Rainier Volcano


If you were ever to visit or move to Seattle you would notice the tallest peak in the Cascade Mountains and that is Mount Rainier. Though it looks like a very tall mountain it is actually an active volcano. The Mount Rainier Volcano is the 21st in the list of the most prominent mountains in the world and it stands at 13,211 feet from its low point. It is also the most prominent mountain found in the lower continental United States. From peak of the Mount Rainier Volcano you can actually see another famous volcano in the area which is Mount St. Helens and you can also get a good look at Mount Adams, Glacier Peak, Mount Baker and Mount Hood.


The Mount Rainier Volcano is what is known as a giant stratovolcano and though it looks quiet it is still considered an active volcano. The last eruption from Mount Rainier took place in 1894 and it has been determined that the volcano has erupted at least a dozen times in 2,600 years. Its largest eruption took place close to 2,200 years ago. Due to the fact that the Mount Rainier Volcano is considered an active volcano there are several smaller high frequency tremors in the area. A lot of times the tremors take place every day. Each month there is a possibility of as many as five quakes taking place at the summit. According to scientists studying the mountain those earthquakes take place due to fluids which circulate inside Mount Rainier.


The Mount Rainier Volcano has two volcanic craters that overlap at the summit. Each one of these craters is over 1,000 feet around. There is also a small crater lake that can be found and that is 130 feet long and it has a 16 foot depth. This lake is the highest one in the continent when it comes to crater lakes. However, that lake is underneath 100 feet of ice and you can only reach it by going through a network of caves made of ice.


The main danger that the Mount Rainier Volcano presents is that it is very close to a highly populated area. The Seattle-Tacoma region could be in grave danger should the volcano erupt again. At the moment scientists do not believe that there will be an eruption anytime soon but that could change as after all it is an active volcano. The population from both Seattle and Tacoma, in addition to the surrounding areas, adds up to close to 3.2 million people and evacuation would present challenges. Another problem is that the volcano is covered with ice. Because of that the USGS (US Geological Survey) has called Mount Rainier “potentially the most dangerous” volcano in the mainland US.

If an eruption took place at the Mount Rainier Volcano the ice on top could create lahars which are a volcanic mudflow that happens when rocks, lava and gas melt ice and create superheated slurry. When an eruption took place 5,600 years ago two of these giant lahars made their way and reached Puget Sound which pushed out the shoreline several miles. That possible danger is what makes Mount Rainier one of only two Decade volcanoes in the US.


One of the best tools which geologists and other scientists have to predict volcanic activity is historic data. Unfortunately the Mount Rainier Volcano has not been very predictable. In fact, it could be called erratic for at least 1,000 years. Even so there are few volcanoes in the United States that are more monitored than Mount Rainier. The monitoring of Mount Rainier is done by the United States Geological Survey together with the University of Washington. Any potential hazards from the volcano’s activity will be assessed by those two entities. There are also plans to minimize any population growth in the area wherever it is possible, especially within the hazard zones. A response plan has been developed but due to the vast amount of people in the area it can be hard to put in place.

Facts About Mount Rainier

The name of the Mount Rainier Volcano was given by George Vancouver and it was in honor of Admiral Peter Rainier. There is a Native American name for Mount Rainier and that is Tahoma which means “the mountain that was God.” The peak of the mountain was not reached until August of 1870 by Hazard Stevens and by P. B. Van Trump. The area was designated a National Park in 1899 and every year 2 million people visit the area. Though it looks very close to Seattle it is actually located 87 miles away. Tacoma is a bit closer at only 65 miles and several smaller towns are even closer. Though the volcano is not considered very active at the moment other eruptions in other areas in the world are giving scientists clues about what to expect from Mount Rainier.

Location Map

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Mount St.Helens Volcano


Mount St. Helens is found in Skamania County in Washington State and is one of the active stratovolcanoes of the world. Its location in Skamania County puts it 50 miles to the northeast of Portland and 96 miles to the south of Seattle. This volcano is part of the Cascade Range and during the current Holocene period, it has actually been the most active in this range. In addition to being the most active, scientists predict that it is the most likely to erupt of all of the volcanoes found in the United States. The volcano has an elevation of 8,363 feet and contains a horseshoe-shaped crater which developed during its most famous eruption in 1980.

Early History

Mount St. Helens has been active for around 275,000 years during which time it has experienced all sorts of volcanic activity ranging from quiet lava outpourings to violent explosive eruptions. During the previous few thousand years Mount St. Helens finally reached the elevation of 8363 feet (before had 9,677 feet) which made it the fifth tallest peak in Washington. It reached its current height after the eruption in 1980 due to an avalanche.

Volcanologists have divided the volcano’s activity into four stages: Ape Canyon (275 – 35 thousand years ago), Cougar (28 – 18 thousand years ago), Swift Creek (16 – 12.8 thousand years ago) and Spirit Lake (3.9 thousand years ago – present). Because each stage changes the composition of the volcano, destroying evidence of previous stages in the process, more is known about the more recent stages than the older ones.

Semi-Recent Eruptive Periods

The Sugar Bowl Eruptive Period took place between 850 and 900 and during this time, three lava domes developed on Mount St. Helens’ flanks. Despite these additions, there was no significant change to the volcano’s appearance during this period.

The Kalama Eruptive Period took place between 1479 and 1720 and this period is when Mount St. Helens achieved its pre-1980 height and form as around 1,600 feet of elevation were added to the volcano during this period. In the beginning of this period there were two large and explosive eruptions which took place in the years 1479 and 1482, a rare phenomenon as those dates are very close together. The early part of this period also produced many pyroclastic flows and lahars. The middle phase began around 1510 and during this point there were few lava flows but many pyroclastic flows. The Summit Dome grew during the late phase of the Kalama Period at Mount St. Helens and most likely took around 100 years to be created.

The Goat Rocks Eruptive Period at Mount St. Helens took place from 1800 to 1857 and this is when the Floating Island, a lava flow in 1801, was created. Scientists believe that the last significant eruption during this period (and in fact until 1980) took place in 1857 although there minor explosions in 1898, 1903 and 1921.

1980 Eruption

The eruption of Mount St. Helens in 1980 is probably the most well-known for this volcano. The first eruption in that group occurred on March 27th and was the first in more than 100 years. Eruptions continued, occurring about once an hour during March and going down to about once a day by the 22nd of April. Eruptions then paused until May 7th at which point small eruptions occurred until the 17th. Mount St. Helens had experienced over 10,000 earthquakes, causing the north flank to grow about 250 feet. This bulge kept growing, indicating a pool of magma that would erupt in the future.

The magnitude 5.1 earthquake mentioned above occurred on May 18th at which point both the summit and the northern bulge became a large landslide. This was in fact the largest avalanche of debris ever recorded in Earth’s history with a total volume of around 3.3 billion cubic yards. The landslide removed the northern flank of Mount St. Helens which in turn triggered a huge lateral blast of hot debris that traveled at around 300 miles per hour. The change in pressure caused a 9 hour long eruption that included a tall eruption column as well as many pyroclastic flows and a great deal of ash fall. The eruption also created lahars (volcanic mudflows) when the snow and ice that had topped the volcano melted and mixed with the volcanic debris.

Mount St. Helens – Future Eruptions

Although this volcano is the most likely one in the Cascades to erupt again within our lifetime, experts do not believe it will be as damaging as the eruption of 1980. They do not think that a lateral blast or such a large avalanche of debris is likely. The main hazards for renewed activity on the volcano are lahars, explosive eruptions causing pyroclastic flows and a continuation of the growth of the lava-dome. Because scientists are not able to predict the next eruption very far in advance, they are keeping close tabs on the volcano using a wide range of geological equipment.


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