• Where can I learn more about the webicorders?

  Our webicorder explanation page is here: http://www.avo.alaska.edu/webicorders/

• What do the color codes mean?

  Go here: http://volcano.wr.usgs.gov/activity/alertsystem/icons.php

• Why don't the webcams take pictures all of the time?

  The webcams are remote installations, and depend on battery power for image capture and transmission. Therefore, we conserve battery life by not turning the camera on during times of inactivity or darkness. We can change the picture interval for Redoubt's Hut cam at a moment's notice, and will do so if the seismicity warrants. Also, please remember that sunrise near Redoubt is not until ~9 am AST, and sunset is around 5:30 pm AST. AST is 1 hour behind PST, 2 hours behind MST, 3 hours behind CST, and 4 hours behind EST.

• Is there "live coverage" of Redoubt?

  There is no video coverage of Redoubt, because it is not near any power generation facilities. Our webcams and satellite monitoring efforts provide intermittent still images. Our seismometers do provide constant coverage, and we are actively monitoring Redoubt around-the-clock.

• How can I sign up for email alerts?

  We do make alerts available over email, however, because of the very large number of recipients, it tends to be a much slower way of learning about changes in activity. To receive AVO alerts as quickly as possible, we encourage people to follow our RSS feed or our twitter feed.

  If you'd just like to follow Redoubt's activity from afar, we recommend signing up for our RSS feed: http://www.avo.alaska.edu/caps/cap_rss.xml to receive our formal information products, or our twitter feed http://twitter.com/alaska_avo to receive our informal "latest observations."

• I'm a member of the press - how can I get an interview with AVO?

  You can call our operations facility at 907-786-7497.

• Where can I learn more about RSAM?

  Our RSAM explanation page is here: http://www.avo.alaska.edu/rsam/

• I have a question about other volcanism in Alaska - where can I find more information?

  Please try these pages: http://www.avo.alaska.edu/volcanoes/about.php, http://www.avo.alaska.edu/faq.php, http://www.avo.alaska.edu/volcanoes/index.php

Beginning Sunday March 22, 2009) at approximately 22:38 AKDT, Redoubt Volcano produced a series of five explosive eruptions that each lasted from four to thirty minutes. The last one ended at 5:00 AM AKDT this morning (March 23). National Weather Service radar, pilot reports, and AVO analysis of satellite imagery suggest that these events produced ash clouds that reached 60,000 ft above sea level (asl), with the bulk of the ash volume between 25 - 30,000 ft asl. Traces of ash fall have been reported in Skwentna, Talkeetna, Wasilla, and Trapper Creek.

AVO remains at Avation Color Code RED and Alert Level WARNING. Seismic unrest continues at Redoubt in the form of elevated volcanic tremor. NEXRAD radar data show that the last significant ash emission was concurrent with the final explosive event at 5:00 AM AKDT. Since that time, no ash has been visible in radar, suggesting that if ash emission is occurring, it is below approximately 13,000 ft asl and/or too fine to be detected. Poor weather at the volcano currently hinders visual observations.

Last night's explosive eruptions caused melting of the Drift glacier and greatly increased discharge down the Drift River. AVO plans a helicopter overflight to the area today to assess conditions at the volcano and along the Drift River. The explosions also destroyed one seismic station near the volcano's summit (RSO), and disrupted telemetry from AVO's obsveration hut. This telemetry outage affects the web camera, a continuous GPS station, and two broadband seismic stations. Repairs to this data link will be undertaken as conditions permit. Seven telemetered seismic stations surrounding Redoubt remain in operation.

The eruptions were preceded by approximately 60 hours of elevated seismicity in the form of discrete earthquakes under the volcano. AVO raised the Aviation Color Code/Alert Level from YELLOW/ADVISORY to ORANGE/WATCH on Saturday, March 21 at 22:09 AKDT. This increase in seismicity likely reflected the upward movement of magma towards the surface. Prior to this weekend, Redoubt had exhibited signs of volcanic unrest beginning in the Fall of 2008 which then escalated in late January, 2009. Last night's explosions were the first significant ash-producing eruptions of the unrest.

Further explosive activity could occur with little or no warning, and could occur intermittently for weeks or months. AVO remains staffed 24 hours per day will issue further information as it becomes available.

For up-to-date Ashfall Advisories and wind trajectories, please refer to the National Weather Service website: http://pafc.arh.noaa.gov/volcano.php

Seismic activity at Mount Redoubt increased at about 1:05 AKDT Sunday afternoon (March 15, 2009) and approximately 4 hours of continuous volcanic tremor ensued. The onset of the tremor was associated with a small explosion that produced a plume of gas and ash that rose to about 15,000 feet above sea level and deposited a trace amount of ash over the summit-crater floor and down the south flank of the volcano to about 3,000 feet. AVO responded to this increase in activity by raising the color code and alert level to ORANGE/WATCH at 2:50 PM AKDT. At this time it does not appear that the increase in activity heralds a significant eruption in the short term, but conditions may evolve rapidly.

An AVO overflight Sunday witnessed activity from 11:30 AM until about 3:00 PM and was able to document ash emission from a new vent, just south of the 1990 lava dome and west of the prominent ice collapse feature near the north edge of the summit crater. Although ash emission was short lived, it represents the first documented ash fall during the current episode of unrest at Mount Redoubt.

About twenty minutes after the initial steam and ash burst, a sediment-laden flow occurred from a small area in the ice at about 7000 feet on upper Drift glacier. This flow descended about 1500 feet and produced a distinctive seismic signature seen across the Redoubt network.

Although the intent of the overflight was make airborne gas measurements, only a few such measurements were possible due to the uncertain nature of the activity and potential for further ash emission. The measurements that were made indicated at least a qualitative increase in SO2 emission relative to levels measured previously. The gas data are currently being processed and will be available soon.

Interpretation of New Activity and Possible Outcomes

Although preliminary, it is likely that the plume observed just after 1:00 PM AKDT on Sunday, March 15, 2009 was produced by a steam explosion in the shallow hydrothermal system of the volcano. Without examination of the ash we cannot say with certainty if the ash represents new magma or if it is merely pulverized old material from the surface of the volcano.

Steam-driven explosions are not unexpected events at Redoubt given the amount of heat that is being released at the surface. It is possible that more such explosions can occur with little or no warning. It is possible that these plumes can reach above 20,000 feet, and may contain minor amounts of fine ash.

Relatively rapid increases in seismic activity, and an overall waxing and waning pattern to the seismicity at Redoubt may persist for weeks to months. Increases in seismicity may or may not be associated with other volcanic phenomena, such as minor ash emission, and vigorous steaming. The burst of activity at Redoubt on March 15, 2009 indicates that the volcano is still in a restless condition.

AVO plans to visit Redoubt later this week to attempt collection of ash samples, retrieve GPS data and do some routine maintenance of seismic and other equipment.

AVO has resumed 24 hour per day staffing of the AVO operations center in Anchorage.

On the basis of declining seismicity, a possible decrease in heat flux, and no apparent change in gas emission, the likelihood of an eruption of Mount Redoubt within days to weeks has diminished. Accordingly, AVO lowered the alert level to YELLOW/ADVISORY on Tuesday, March 10, 2009, and ceased round the clock staffing of the AVO operations center. The volcano remains on a heightened monitoring schedule, and AVO scientists will continue to evaluate conditions at the volcano regularly. The volcano remains restless and it is still possible, though far from certain, that the current episode of volcanic unrest at Mount Redoubt could result in an eruption.

Over the past two weeks the overall level of seismic activity has decreased, and the periods of sustained volcanic tremor, common during late January and most of February, have been largely absent. Discrete earthquakes are still occurring, but they are typically small and their observed rate is similar to that detected prior to this period of unrest. Volcanic gas emissions are still well above background levels, and melting of the upper Drift glacier in the vicinity of the 1989-90 eruption vent is continuing. These conditions could persist for many months and do not indicate that an eruption is imminent. It remains possible for conditions at the volcano to change rapidly, advancing from relatively low levels of unrest to eruption in time periods as short as 24 hours. If this happens, seismic activity should increase markedly providing some advance warning. At the present time, the overall trend is one of declining unrest and a much lower probability of an eruption in the near term.

Chronology of Unrest

November 5, 2008: Volcano alert level raised to YELLOW /ADVISORY in response to elevated gas emissions and visual evidence of ice melt in the volcano's summit crater. Reports of sulfur smell in the vicinity of the volcano as early as August, 2008.

January 25, 2009: Volcano alert level raised to ORANGE/WATCH in response to a sudden and distinctive increase in seismicity beneath the volcano.

January 25 - February 26, 2009: Observations and measurements of snow and ice melt, minor flooding, debris flows, and steam emission in the upper Drift glacier area. During this period, elevated levels of volcanic gas (CO2, SO2, and H2S) were detected by airborne measurements. The nature of the gas emissions indicated a magmatic source. Seismic activity during this period was characterized by frequent discrete earthquakes and episodes of strong, continuous, volcanic tremor that also was detected at seismic stations as far as Mounts Spurr and Iliamna (45 to 90 km distant). No ash emissions were observed. Steam plumes were occasionally observed rising to about the summit of the volcano.

February 26 - March 10, 2009: During this period, the overall level of seismic activity decreased and episodes of sustained volcanic tremor were largely absent. Discrete earthquakes are still occurring; however, most are small and similar to those detected during normal background activity. Volcanic emissions and snow/ice melt continue, occasional steam plumes observed by web camera.

March 10, 2009: AVO lowers the volcano alert level to YELLOW /ADVISORY in response to declining seismic activity. The AVO operations center in Anchorage has ceased 24 hour staffing. However, AVO staff continues regular surveillance of the volcano by the web camera, overflights, airborne measurements of gas output, seismic analysis, and examination of satellite data.

Analysis of Unrest

The current episode of unrest is most likely a result of intrusion of new magma beneath the volcano. The main evidence for an influx of new magma is: (1) measurement of significant amounts of magmatic gas, including CO2, SO2, and H2S from fumaroles in the vicinity of the 1989-90 vent; (2) increased heat flux causing ice/snow melt of the upper Drift glacier (about 4-5 million cubic meters through March 10, 2009), and fluctuating water discharge from streams draining the lower Drift glacier, (3) elevated seismicity since January 23, 2009, including hour-long periods of continuous volcanic tremor that is consistent with the movement of fluids (including heated ground water) and gases within the volcano. The influx of magma and rise of hot magmatic gases resulted in a reinvigoration of the volcano's hydrothermal system and this activity was likely the cause of some of the shallow seismicity. The increased heat output caused melting and disruption of snow and ice on Drift glacier and this led to greater than normal water outflow and at least one sediment-water outburst flood on Drift glacier.

Although we do not know how much new magma has intruded beneath Mount Redoubt, we estimate that most of the new magma is probably at depths greater than about 5 km (about 3 miles). It is possible that a small amount of the magma may have risen to shallower depths in late January-February when seismicity, degassing, and melting intensified. There is no evidence indicating a large volume of magma is present at shallow depths (within 2 km, or about a mile, of the surface).

On the basis of reduced seismic activity, it appears that the new magma intruded beneath the volcano is no longer moving toward the surface, or is doing so at a greatly reduced rate. Thus the probability of an eruption of Mount Redoubt within days to weeks is low. The volcano remains in a restless condition and it is still plausible that the unrest observed thus far will lead to an eruption on a longer time scale. We expect that elevated levels of volcanic gas emission and additional melting of the upper Drift glacier will continue for some time, perhaps many months.

Potential Future Activity

Redoubt is an active volcano and future eruptions are a certainty. The 1989-90 eruption was seismically monitored, but little was known about the seismic behavior of the volcano prior to that eruption. It is uncertain if future activity will be more or less like that of 1989-90. In 1989, seismic activity escalated rapidly, and explosive events occurred after only about 24 hours of precursory seismicity. During the current unrest, the sudden onset of strong volcanic tremor on January 25, 2009 was preceded by about two days of elevated seismicity, and the tremor indicated an eruption of Redoubt appeared likely. The activity observed thus far is distinctly unlike the activity that preceded the 1989-90 eruption, and has implications for future unrest and possible eruptive behavior.

Based on our observations and understanding of Redoubt Volcano to date, AVO considers the following scenarios as possible outcomes of the current period of unrest.

1. Gradual decline in earthquake activity, gas emission, and heat output, and return to normal background conditions. Occasional periods of slightly elevated activity that abates. Period of unrest ends, no eruption occurs.
2. After a period of relative quiescence, lasting some weeks to months, seismic activity increases, possibly rapidly, and the possibility of an eruption becomes more likely. The increase in seismicity likely would be accompanied by increasing volcanic gas emission, snow and ice melt, and increased melt-water runoff. If this situation arises, the following outcomes are plausible:

   a. Hydrothermal system becomes invigorated, and this increases the possibility of phreatic activity (water related steam emissions or steam explosions), or explosive phreatic eruption. This could lead to magmatic involvement and an explosive magmatic or phreatomagmatic eruption.

   b. Explosive eruption occurs, associated with rapid assent of magma to shallow levels. Activity could be similar to that of 1989-90 and may occur after a brief period of precursory seismicity, possibly as short as 24 hours.

   c. Hydrothermal system becomes invigorated as it did in January-February, 2009, but again does not culminate in eruptive activity.

At present, AVO regards both scenarios 1 and 2 as about equally likely, and gives equal relative probability to scenarios 2a, 2b, and 2c should conditions evolve toward scenario 2. There are several examples worldwide of an explosive eruption occurring many months to more than a year following the onset of increased heat output. In fact, the 1966 eruptions of Redoubt occurred a year following the onset of increased steaming observed at the summit.

Ongoing Hazards at Current Level of Unrest

Heat and volcanic gas output could gradually decline over the coming months. However, parts of upper Drift glacier were disturbed by melting, and readjustment of the glacier will occur over time. Rapid settling of the ice could initiate sudden onset, fast moving and potentially hazardous outflows of water and sediment in the drainages adjacent to and downstream of Drift glacier. It is possible that settling of the ice may also initiate ice and rock avalanches, or unusual water flow on the surface of Drift glacier. These flows of water and or ice would be hazardous to anyone on Drift glacier or along its outflow streams.

If the hydrothermal system remains active for some time, additional melting, ice collapse, and minor downstream flooding should be expected. It is also possible that stream-driven (phreatic) explosions may occur without warning and it is possible for such explosions to produce plumes (possibly containing fine rock fragments) that could rise well above the summit of the volcano. Volcanic gas emissions are likely to continue for some months, and sulfur odors could be noted by people in the region. The output of volcanic gas will likely decline, but emission rates could be variable. During low wind conditions, potentially hazardous levels of gas could accumulate in low lying areas in the Drift glacier drainage.

On the basis of current activity, the Alaska Volcano Observatory (AVO) continues to expect that the most likely outcome of current Redoubt activity is an eruption, similar or smaller in scale to the 1989-1990 eruption. It is not currently possible to determine exactly when such an eruption might occur. Based on observations of past eruptions of Redoubt, ongoing analysis of the current activity, and studies of similar volcanoes worldwide, the current period of elevated unrest could persist for some time, possibly many months. However, as long as substantial volcanic-gas emission, prolonged periods of tremor, and intermittent discrete, shallow earthquakes occur, notable escalation of activity immediately prior to an eruption might only be on the order of hours or less.

The alert level remains at ORANGE/Watch, and for the time being AVO is staffed 24/7. If seismicity or other monitoring data suggest that Redoubt may be rapidly escalating to an eruption, AVO will send out a notification.

Monitoring Summary

Unrest at Redoubt Volcano continues; no eruption has yet occurred.

Redoubt Volcano has been at elevated alert levels for the past three months. AVO raised the aviation color code to YELLOW and the alert level to ADVISORY on 5 November 2008 in response to elevated gas emissions and visual evidence of melting of ice near the volcano's summit crater. AVO raised Redoubt's aviation and alert levels to ORANGE/WATCH on 25 January 2009 in response to a sharp increase in seismicity detected beneath the volcano. Since 25 January 2009, AVO also has detected corresponding increases both in the rate of glacial melting and of magmatic gas emissions at the volcano's summit.

The Observatory facility in Anchorage currently is staffed 24 hours a day. AVO staff continues to conduct visual surveillance of the volcano via the web cam and overflights, airborne measurements of gas output, seismic analysis, and examination of satellite and weather-radar data.

In response to this elevated unrest, AVO has: conducted ten overflights of the volcano to make visual observations and gas measurements; installed a web camera, two more seismic stations, and a GPS sensor close to the volcano; redirected a webcam on a platform in the Cook Inlet to view Redoubt; assisted in the installation of lightning-detection equipment on the Kenai Peninsula, and improved the telemetry system that transmits data to the Observatory. Additional upgrades of the Redoubt monitoring system, water sampling, and overflights for observation and gas measurements are planned over the next several weeks as weather permits.

Analysis of Current Unrest

Analysis of monitoring data suggests that the current episode of unrest results from the intrusion of new magma beneath the volcano. The main evidence for the presence of this magma is: (1) measurement of substantial amounts of magmatic gas (thousands of tons per day of carbon dioxide) being emitted from the volcano's summit area; (2) visual observations of high heat flux such as intermittent steam plumes, melting of the upper Drift Glacier (as much as 5-6 million cubic meters through February 10), and increased water discharge from the lower Drift Glacier, (3) elevated seismicity since 23 January 2009, including continuous shallow tremor that is consistent with the movement of fluids (including heated ground water) and gases within the volcano, and (4) deep earthquakes in December 2008 and January 2009 that may have marked magma movement.

Comparison to Previous Periods of Volcanic Activity at Redoubt

There are few past examples of Redoubt eruptions that were well-monitored or well-observed. In 1965-1968, incomplete accounts indicate that elevated levels of unrest occurred for months before the onset of eruptive activity. In 1933, activity of Redoubt may have consisted only of a temporary increase in gas and heat output and no eruption.

The 1989-90 eruption is the only one that was seismically monitored, and seismic stations were emplaced mere months prior to the start of the eruption. Prior to the first explosive events in 1989, precursory seismicity ramped up quickly over a period of 23 hours. The eruption lasted from December 1989 until June 1990, and was characterized by explosive events that produced ash clouds reaching as high as 40,000 ft above sea level, separated by periods when lava domes grew in the summit crater. During the 1989-90 eruption, ash fall was greatest on the Kenai Peninsula, reaching a few (3-5) millimeters (0.1-0.2 inches) on one occasion, with trace amounts deposited in Anchorage and other communities in south-central Alaska. Ash clouds from the 1989-90 eruption also disrupted air traffic operations in and out of the Anchorage area and Kenai. Mudflows, formed as hot erupted material swiftly melted large volumes of snow and ice mantling the volcano, traveled down the Drift River and reached Cook Inlet, partially flooding the Drift River Oil Terminal facility.

Heavily ice-mantled Redoubt Volcano is located on the western side of Cook Inlet, 170 km (106 mi) southwest of Anchorage and 82 km (51 mi) west of Kenai, within Lake Clark National Park. Redoubt is a stratovolcano which rises to 10,197 feet above sea level. Recent eruptions occurred in 1902, 1966-68, and 1989-90.

Since last fall, the Alaska Volcano Observatory (AVO) has detected increasing volcanic unrest at Redoubt Volcano. Starting on Friday, January 23, the level of seismic activity increased markedly, and on Sunday AVO raised the Aviation Color Code to ORANGE and the Volcano Alert Level to WATCH. On the basis of all available monitoring data AVO regards that an eruption similar to or smaller than the one that occurred in 1989-90 is the most probable outcome. We expect such an eruption to occur within days to weeks.

In response to the current increase in activity, AVO has deployed a web camera approximately 7.5 miles north-northwest of the summit and will install additional seismic equipment at the volcano as weather permits. A second web camera also is pointed at Redoubt from a platform within Cook Inlet. The observatory in Anchorage is currently staffed 24 hours a day. We plan continued visual surveillance of the volcano's summit region, frequent airborne measurements of gas output, and frequent analysis of satellite and weather-radar data.

Observations and Background

Beginning in September 2008, AVO received reports of a strong hydrogen sulfide (H2S) odor downwind of Redoubt. During an observation flight on September 26, a melt hole was observed in the upper Drift glacier, down slope from the location of historical eruptive vents. Gas-measurements flights in October and November detected elevated levels of sulfur dioxide (SO2), carbon dioxide (CO2), and H2S. Through the fall, melt holes increased in size, and several points of steaming and gas emissions were observed in the area of the lava domes extruded during the 1989-90 and 1966-68 eruptions.

Concurrent with visual observations and gas data, a subtle increase in seismic activity was also detected beneath the volcano. Seismicity took the form of episodic, very weak volcanic tremor, consistent with the movement of fluids and gases within the volcano. AVO also located deep (30 km, or 19 miles, below sea level) long-period earthquakes, which were few in number but possibly indicative of magma recharge deep within Redoubt's plumbing system.

Beginning on the evening of Friday, January 23, 2009, seismic activity increased at stations closest to Redoubt's summit. The seismicity consists of a combination of discrete, relatively small earthquakes and periods of more continuous volcanic tremor. This activity intensified early Sunday morning, January 25, at which time AVO raised the Aviation Color Code to ORANGE and the Volcano Alert Level to WATCH. Since Sunday, seismicity has waxed and waned but has remained well above background levels. The seismic unrest observed over the past few days is unusual for Redoubt and has not been seen since just prior to the 1989-90 eruption. Overflights on January 26 and 27 documented continued production of water vapor and volcanic gas plumes from the summit crater; increased melting has produced small flows of debris at the north base of the volcano.

The most recent eruptions of Redoubt, in 1966-68 and 1989-90, were characterized by large explosions that produced ash clouds reaching as high as 40,000 ft asl. During the 1989-90 eruption, the largest ash fall from a single event in Kenai was 5 millimeters (0.2 inches), but ash fall was widespread and noted as far away as Fairbanks, along the Richardson Highway, and the Yukon Territory border. Other ash-producing events during the 1989-90 eruption deposited several millimeters of ash on the Kenai Peninsula and trace amounts of ash in Anchorage and more distant locations over several months. The 1989-90 eruption also several disrupted air traffic operations in and out of Anchorage. Other hazards from past and likely future eruptions include hot pyroclastic flows that may travel several miles from the volcano, especially to the north, and volcanic mudflows, or lahars, that travel many miles from their source. Lahars form as hot pyroclastic flows, often caused by collapse of a growing lava dome, swiftly melt large volumes of snow and ice downslope of the summit crater. In 1989-90, lahars flowed east down the Drift River, at least three of which reached Cook Inlet and one of which partially flooded the Drift River Oil Terminal facility. Lahars produced by eruptions of Redoubt Volcano may range from dense, gravel-rich flows to watery, sediment-laden floods. All such flows can transport boulder-size particles, and water within these flows temporarily may be at boiling temperatures. It could take a typical lahar 1-2 hours to travel from the base of the volcano to the mouth of the Drift River.