🌋VolcanoAtlas

Redoubt Volcano

Alaska's Aviation Hazard Sentinel

Elevation

3,108 m

Last Eruption

2009

Type

Stratovolcano

Country

United States

Location

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Volcanic Hazards & Risk Assessment

Primary Hazards

  • Pyroclastic flows
  • Lava flows
  • Volcanic bombs and ballistics
  • Lahars and mudflows

Risk Level

Population at RiskModerate
Infrastructure RiskHigh
Aviation RiskSignificant

Geological Composition & Structure

Rock Types

Primary
Unknown
Silica Content
Varied composition

Tectonic Setting

Unknown
Intraplate setting with hotspot or regional volcanic activity.

Age & Formation

Epoch
Unknown
Evidence
Unknown

Eruption Statistics & Analysis

MetricValueGlobal RankingSignificance
Total Recorded EruptionsUnknownLowModerately active volcano
Maximum VEIVEI UnknownMinorLocal impact potential
Recent Activity17 years agoRecentRecently active

Monitoring & Alert Status

Monitoring Networks

USGS Volcano Hazards Program
Comprehensive monitoring network
Global Volcanism Program
International eruption database

Current Status

Watch
Dormant but monitored. Capable of renewed activity.

Authority Sources

Smithsonian GVP
Official volcano database
USGS Volcano Hazards
U.S. Geological Survey

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Interesting Facts

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KLM Flight 867, a Boeing 747 with 245 people aboard, lost all four engines after flying through Redoubt's ash cloud in December 1989 — the pilots restarted the engines after a 4,000-meter powerless descent.

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The 1989–1990 eruption caused over $160 million in damages, primarily to the Cook Inlet oil industry and aviation sector.

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Redoubt has 99 recorded eruptions spanning more than 11,000 years, making it one of the most active volcanoes in the Aleutian arc.

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A catastrophic summit collapse between 13,000 and 10,500 years ago sent a debris avalanche all the way to Cook Inlet, approximately 35 km from the summit.

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The Drift River Oil Terminal, located in Redoubt's lahar hazard zone, stores millions of barrels of crude oil and has been threatened by lahars in every historical eruption.

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The 2009 eruption produced 19 distinct explosive events in just two weeks, with ash columns reaching 15 km (50,000 ft).

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Redoubt is visible from Anchorage (population ~290,000) on clear days, lying approximately 170 km to the southwest across Cook Inlet.

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The 1989 eruption was directly responsible for the creation of the international Volcanic Ash Advisory Center system, which now protects global aviation.

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Every historical eruption of Redoubt has been rated VEI 3, suggesting that moderate explosive activity with dome growth is the volcano's characteristic behavior.

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The volcano sits within Lake Clark National Park, one of the least-visited national parks in the United States, with no road access.

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Redoubt's construction began approximately 890,000 years ago over Mesozoic granitic basement rocks of the Alaska-Aleutian Range batholith.

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The name 'Redoubt' comes from the volcano's fortress-like appearance when viewed from Cook Inlet — 'redoubt' is a military term for a defensive fortification.

Frequently Asked Questions

Is Redoubt Volcano still active?
Yes, Redoubt is classified as an active volcano by the Alaska Volcano Observatory (AVO). It last erupted in 2009, when a four-month-long eruptive episode produced 19 explosive events, pyroclastic flows, lahars, and a lava dome within the summit crater. The volcano has produced four confirmed eruptive episodes since 1902, at an average interval of approximately 20–40 years. AVO maintains continuous seismic, GPS, and infrasound monitoring at Redoubt and currently assigns it a Green (Normal) alert level. Volcanologists consider another eruption in the coming decades to be statistically likely.
What happened to the KLM plane during the 1989 Redoubt eruption?
On December 15, 1989, KLM Flight 867 — a Boeing 747-400 flying from Amsterdam to Anchorage with 245 passengers and crew — flew into an ash cloud from Redoubt at approximately 7,600 m (25,000 ft). All four engines ingested volcanic ash and flamed out. The aircraft descended powerless for nearly four minutes, losing approximately 4,000 m of altitude, before the pilots managed to restart the engines and make an emergency landing at Anchorage. The aircraft sustained over $80 million in damage. This incident was instrumental in establishing the international Volcanic Ash Advisory Center system.
When did Redoubt last erupt?
Redoubt's most recent eruption began on March 15, 2009, and continued through approximately July 1, 2009. The eruption produced 19 explosive events between March 22 and April 4, with ash columns reaching 15 km (50,000 ft). Pyroclastic flows melted glacial ice, generating lahars that traveled down the Drift River valley toward Cook Inlet. A lava dome grew within the summit crater through the spring months. Ashfall reached Anchorage, forcing school closures and disrupting air traffic. The eruption was rated VEI 3.
How tall is Redoubt Volcano?
Redoubt Volcano stands 3,108 m (10,197 ft) above sea level, making it one of the tallest volcanoes in the Cook Inlet region of Alaska. The summit elevation has varied over time as eruptions build lava domes and explosive events destroy them. The glacier-covered peak is visible from Anchorage, approximately 170 km away, on clear days. The 1.8-km-wide summit crater is breached to the north, the result of a catastrophic sector collapse that occurred between 13,000 and 10,500 years ago.
Is Redoubt dangerous to Anchorage?
Yes, Redoubt poses a significant hazard to Anchorage and the surrounding Cook Inlet region. At 170 km distance, Anchorage is within ashfall range during major eruptions — the 2009 eruption deposited measurable ash on the city, disrupting daily life and closing schools. The greater threat is to aviation: Anchorage's Ted Stevens International Airport is a major hub for trans-Pacific cargo flights, and volcanic ash at altitude can cause jet engine failure, as demonstrated by the 1989 KLM incident. Additionally, lahars from Redoubt threaten the Drift River Oil Terminal and could potentially reach Cook Inlet, affecting fisheries and maritime navigation.
What type of volcano is Redoubt?
Redoubt is classified as a stratovolcano (also called a composite volcano), built from alternating layers of lava flows, volcanic ash, and debris over approximately 890,000 years. Its primary rock types are andesite and basaltic andesite — intermediate-composition magmas that produce both explosive eruptions and viscous lava domes. The volcano features a 1.8-km-wide summit crater breached to the north, extensive glacier coverage, and a history of eruptions that combine explosive columns, lava dome growth, pyroclastic flows, and lahars. This combination of hazards makes it a typical but particularly dangerous subduction zone stratovolcano.
Can you visit Redoubt Volcano?
Visiting Redoubt is challenging due to its extreme remoteness within Lake Clark National Park, which has no road access. The most common way to experience the volcano is via scenic flightseeing tours from Anchorage, Kenai, or Homer, which offer spectacular aerial views of the glacier-covered peak, breached summit crater, and 2009 lava dome. On clear days, Redoubt is visible from many locations in Anchorage and the Kenai Peninsula. Mountaineering on the volcano requires advanced glacier travel skills and awareness of volcanic gas hazards. No visitor facilities exist on or near the volcano.
Why is there an oil terminal in Redoubt's lahar zone?
The Drift River Oil Terminal was constructed in the 1960s before modern volcanic hazard assessments fully quantified the lahar risk from Redoubt. The terminal collects oil piped from Cook Inlet offshore platforms and stores it for periodic tanker loading. During both the 1989 and 2009 eruptions, lahars from the volcano flowed down the Drift River valley and inundated the terminal area. In 1989, floodwaters came within a meter of overtopping containment dikes. After the 2009 eruption, significant efforts were made to reduce stored oil volumes during eruptions and develop contingency plans, but the fundamental conflict between the facility's location and volcanic hazard remains a subject of ongoing debate.