Mount Redoubt

Mount Redoubt is a Stratovolcano that is located 103 miles south west of the city of Anchorage in Alaska. this volcano dates back to about 890,000 years ago. This volcano is the most active volcano of all the Cook Inlet volcanoes. Its most recent eruption began on March 22, 2009.
Figure 1: Mount Redoubt heavily covered with deposits from the recent eruptions in March 2009

Background:Mount Redoubt is a glacier covered Stratovolcano that stands about 10,197 feet high and has a breached summit crater created by past eruptions. Redoubt is located in the state of Alaska in Lake Clark national Park. Mount Redoubt is one of 40 active volcanoes in the Aluetian Volcanic Arc which is stretched about 1550 miles across the North Pacific. This volcano is composed of pyroclastic deposits and lava flows that sit on giant Mesozoic granite rocks, and has been moderately dissected by the action of numerous glaciers. Redoubt has the third highest peak within its range trailing only behind Mount Spurr and Mount Torbert. Redoubt has been active for over a millennia and since 1900 has erupted five different times. Before the 2009 eruption the volcano laid dormant for about 20 years, erupting in 1989. The volcano erupted over a four month period between 1989 and 1990 sending a plume of ash, from a plinian type of eruption, into the atmosphere so large that it was able to interfere with air traffic. It was stated at the time that the 1989 - 1990 eruption was one of the highest cost eruptions in United States history. This eruption affected the Drift River drainage to the north and had a severe economic impact of the Cook Inlet regions; both can be seen in figure 2. Redoubt has produced both basalt and andesite lava in its eruptions with andesite being the more dominant lava in the more recent eruptions. The volcano has multiple lahar deposits that stretch as far as the Cook Inlet which can also be seen in figure 2.
Figure 2: Mount Redoubt is shown in the middle with the Drift river leading off to the North and the Cook inlet shown to the East.

Most Recent Activity:
Volcanic tremors started to shake Redoubt once again in early February 2009 that made the Alaskan Volcano Observatory warn the people around that region of four different possible outcomes: either Redoubt was going to go quiet without an eruption or could explode with a large eruption and everything in between.On Sunday, January 25th, 2009, the AVO raised the Aviation Color Code to Orange and the Volcano Alert Level to Watch. These codes mean that the volcano was exhibiting heightened or escalating unrest with increased potential of eruption, though the timeframe was uncertain. Scientist started monitoring the whole February. Also, additional web cameras were installed along with more seismic stations and a sensor close to the volcano. Approximately every three days, planes flew over the mountain to observe activity and to measure gas emission. It was determined that the seismic activity on Mount Redoubt was due to the influx of new magma beneath the volcano. The emission of steam plumes was melting the ice on upper Drift Glacier. The shallow tremors on the mountain were attributed to the movement of ground water, other liquids and gases. On the summit of the mountain, large amounts of magmatic gas were escaping. As learned from class, measure the amount of escape of gas is one of the precursors.On March 15, 2009, volcanic activity resumed and the warning levels were increased to Orange and Warning. Tremors became more frequent and high gas emissions were measured. A plume of ash and steam was also observed.On March 21. 2009, activity increased again. Earthquake activity intensified and a small steam plume was observed at the summit. Round the clock observation resumed. At 10:00pm, the warning levels were put back up to Orange and Watch. Shallow earthquakes were increasing and at times, they were only a few minutes apart. Several small earthquakes is also one of the precursors. This is a short term prediction for this two months.

On March 22 2009, Redoubt started a series of six eruptions in a 24 hour period and sent an ash plume more than 9 miles into the air. Unlike the eruption 20 years earlier though the wind played in the states favor and sent the ash cloud away from Anchorage. Some communities north of Anchorage though did get a fine gray dust that fell down to the ground. The ash that fell from Redoubt is like rock fragments with jagged edges but was so far from and large populations so was not too dangerous for people living in the vicinity but was still very dangerous for air traffic moving through the area. The eruption rapidly melted the ice and snow atop of Redoubt creating muddy waterfalls rushing down the sides of the volcano as seen in figure 3. These waterfalls if structures were built close to the volcano could cause great damage and be very destructive to anything in their path.The material ejected from the volcano mainly consisted of water vapor, along with smaller amounts of carbon dioxide and sulfur dioxide. This is a Vulcanian type eruption. It had viscous magma and gas emission, it had alternative between lava and masses of blown out of ash, and the ash covered wide area.

Figure 3: Shows muddy waterfalls flowing down the side of the volcano as a result to the melting snow and ice atop Redoubt.

Recent Eruption's Impact on the Population:
From the volcano's most recent eruption which sent an ash plume more than 9 miles into the air in its first emissions in nearly 20 years 19 Alaska Airlines flights were canceled and four other flights from smaller airline companies were also canceled. This was because the ash can harm the engines of the planes . Five of the 20 Alaska state senators were scheduled on the morning flight from Anchorage which was canceled and as a result consideration of different legislation was delayed including a resolution accepting federal stimulus funds. The wind happened to be playing in Alaska's favor this time though and took the ash cloud away from Anchorage toward Willow and Talkeetna, near Mount McKinley. The ash from the volcano can cause skin irritation and breathing problems, but was so far from any population that it was not too dangerous for people living in the vicinity but was still very dangerous for air traffic. Still, people with respiratory problems were asked to not go outside of their homes or if they had to do so to wear a face back, until the ash calmed down. The Alaska observatory was working very closely with the Federal Aviation Administration and the National Weather Service to track ash clouds and ensure flights were diverted or canceled if necessary. Dozens of aircraft at the Elmendorf Air Force Base in Anchorage were being sheltered as a precaution against the falling ash. In rural areas, people also suffered from cancelations of air transportation. At Talkeetna Air Taxi, flights were canceled and air planes were covered to protect them from the falling ash.
After the series of the Mount Redoubt eruptions started on Marh 22, the Drift River Terminal was closed and evacuated. Coast Guard officials came up with an agreement to move about 6.3 gallons of crude oil from the Drift River Terminal, which is at the foot of Mount Redoubt, for fear of experiencing an oil spill. This might have also been due to the threat of dome collapse, pyroclastic flows, lahars, and floods. However, after the oil is removed there will still be a large quantity of it left on the tanks. After the eruption of Redoubt in 1989-90, the terminal was improved by adding dikes to it to keep it safe from the damage of floods and lahars going down the Drift River valley from Redoubt, which have proved to be a success because they have been resistant during the present floods. Notwithstanding this, the main reason for the removal of the oil is the people’s concern in having an oil terminal near an active mount. Luckily this most recent eruption, unlike the eruption nearly 20 years before, did not have a very big impact on the population. The biggest hurtle that the Alaskan population had to overcome was the air traffic barrier. Almost all of the population was not greatly affected by the eruption. There was a light fall on the large cities, but it was only very light ash. The main ash flow was taken by the wind away from any larger populations. In other places the aftermath of the eruptions was more obvious. In the town of Skwentna, trees and snow were turned black by the ash.

Figure 1:
Figure 2:
Figure 3:,2933,510100,00.html

Klemetti, Erik. “Oil from the Drift River Terminal near Redoubt to be moved.” 3 April 2009. 17 March 2010

Mauer, Richard. “Volcano Status Lowered; Oil to be Moved.” Anchorage Daily News. 4 April 2009. 17 March 2010 <>.

Riccardi, Nicholas and Stuart Glascock. “Alaska's Mt. Redoubt Erupts Five Times Overnight.” Los Angeles Times on the Web 24 March 2009. 17 March 2010 <>.

“Volcano in Alaska Blows Top Again.” BBC News. 24 March 2009. 17 March 2010.