Pavlof Volcano

Ash Plume from Pavlof's 2007 Eruption

Pavlof ash plume: Pavlof Volcano and an eruption plume photographed from a commercial flight on August 30, 2007. The plume is about 17,000 feet tall. Little Pavlof is the smaller peak on Pavlof's right shoulder. Eruptions like this are a severe hazard to local and international air traffic. Photograph by Chris Waythomas, Alaska Volcano Observatory / U.S. Geological Survey.

Pavlof Volcano Introduction

Pavlof is one of the most active volcanoes in North America. Sometimes Pavlof erupts with very little warning. In the past 100 years, Pavlof has erupted at least 24 times and may have erupted on several other occasions.

A combination of factors - Pavlof's remote location, weather with limited visibility, and very few local inhabitants - may have allowed some eruptions at Pavlof to go unconfirmed. Today, daily satellite monitoring and real-time data from instruments on the ground bring a continuous stream of information to scientists. [1]

Map: Where is Pavlof Volcano?

Where is Pavlof Volcano? A map showing the location of Pavlof Volcano near the end of the Alaska Peninsula. The boundary between the North America Plate and the Pacific Plate is shown by the gray toothed line. The Pacific Plate is to the south of the boundary, and the North America plate is to the north of this boundary. The A-B line shows the location of the cross-section below.

Pavlof's Threat to Air Traffic

Although there is very little human activity on the land immediately surrounding Pavlof, the sky above is heavily travelled. Aircraft from the United States and Canada flying to Asia pass through areas where wind-borne volcanic ash from Pavlof might be carried. Each day thousands of international airline passengers and dozens of flights loaded with freight fly directly above the volcano.

An eruption at Pavlof that puts large amounts of volcanic ash high into the atmosphere produces air traffic safety concerns and significant financial losses while flights must be rerouted. This is why Pavlof Volcano receives so much attention from scientists. [2]

Simplified plate tectonics cross-section

Plate tectonics of Pavlof: A simplified plate tectonics cross-section showing how Pavlof Volcano is located on the North American Plate. The thickened portion of the plate represents the Alaska Peninsula. A subduction zone, formed where the Pacific Plate descends beneath the North America Plate, is directly below the volcano. Magma produced from the melting mantle and Pacific Plate rises to the surface and causes eruptions.

Pavlof Volcano: Plate Tectonic Setting

Pavlof is located near the western end of the Alaska Peninsula. The convergent boundary between the North America Plate and the Pacific Plate is located to the south and east of Pavlof as shown on the map above.

The North America Plate is moving in a southerly direction, and the Pacific Plate is moving towards the northwest. These relative motions produce the collision between the two plates that creates a subduction zone at their boundary.

At this location, both plates consist of oceanic lithosphere. At the plate boundary, the Pacific Plate is forced under the North America Plate to form the Aleutian Trench and a subduction zone. A diagram of this plate boundary situation is shown in the simplified cross-section on this page.

Pavlof's Eruptive Style

Most of Pavlof's eruptions have involved low-energy ash releases, minor andesite lava flows, or minor lava fountaining. These sometimes produce lahars when ash and lava melt portions of Pavlof's snow cap. Some of these lahars have been large enough to reach the Pacific Ocean to the south or the Bering Sea to the north.

Occasionally, Pavlof produces a strong explosive eruption or a number of smaller explosive events in a single eruptive episode. The 1983, 1981, 1974/1975, 1936/1948, and 1906/1911 eruptions produced enough ejecta to be rated at level 3 on the Volcanic Explosivity Index. The 1762/1786 eruption has been rated at VEI 4. [2]

Pavlof's Eruptive History: Chart of the eruptive history of Pavlof Volcano by century. The greater frequency of eruptions over the last two centuries can mainly be attributed to improved observation abilities and greater interest in the volcano. Data in this chart is from the Alaska Volcano Observatory [1], where more specific details for most of these eruptions are available for public view. Some of the eruptions extended in time across two or more calendar years. [1] Volcanic explosivity data is from the Pavlof Volcano Summary at the Smithsonian Institution website. [2]

Pavlof Volcano: Eruptive History

The chart on this page summarizes the eruptive frequency of Pavlof for which there is a written record. The small number of eruptions in the early portion of this record reflects the remote location of the volcano, the lack of local population, and the poor weather conditions that limited observation. Eruption frequencies in the 1700s, 1800s and early 1900s are underrepresented.

Some of the eruptions are marked as "questionable." At times it was impossible to attribute an eruption to a specific volcano because vents are so numerous and close together in the Emmons Lake Volcanic Center. [3]

The eruptive history in the late 1900s and in the 2000s is more complete and accurate. This reflects the availability of satellite monitoring, ground-based monitoring equipment, and a greater interest in the volcano because of its potential impact on air traffic.

Pavlof Ash Plume Animation

Animation of a Pavlof Ash Plume: The animation above shows the production and dispersal of an ash plume released by Pavlof Volcano in December 2021. It shows how an ash eruption can occur suddenly and spread in a broad, rapidly moving plume across the sky. Animation by the United States Geological Survey (more information).

Pavlof Hazard Map

Pavlof Hazard Map: Map showing the geographic extent and locations of pyroclastic flow, surge and blast hazards around Pavlof and neighboring volcanoes. USGS image. Enlarge. Additional maps of lahar, debris-avalanche, ash fallout and other hazards are part of the Preliminary Volcano-Hazard Assessment for the Emmons Lake Volcanic Center report and map set. [4]

Pavlof: Geology and Hazards

Although eruptions at Pavlof have been numerous, they have fortunately been small to moderate in size. They are often Strombolian eruptions that produce local falls of tephra. Pavlof also produces ash plumes that can be carried hundreds of miles by the wind.

Pavlof has not been a deadly threat to people on the ground because very few people venture near the volcano. The nearest community is Cold Bay, about 35 miles to the southwest. Other nearby communities include King Cove, Nelson Lagoon, and Sand Point. All of these are beyond the reach of lahars and pyroclastic flows; however, each of these communities has experienced ashfalls from eruptions at Pavlof.

Ash plumes are the most significant hazard associated with eruptions at Pavlof. They are a major hazard to local aircraft and a threat to international air traffic when they reach significant height. This is why the volcano is monitored with instruments and why satellite images of the volcano are examined daily.

Pavlof is usually covered by snow and ice. Eruptions can quickly melt significant amounts of snow and ice to produce volcanic mudflows known as lahars. These lahars are fast-moving slurries. They can fill stream valleys with hot water, sand, gravel, boulders, and volcanic debris. They destroy stream habitat, which can be lost for many years after an eruption. They travel at very high speeds, and anyone in stream valleys below the volcano when an eruption occurs must quickly move to high ground to escape the deadly flow.

Pavlof eruptions often produce pyroclastic flows. These are hot clouds of rock, gas, and ash that sweep down the flanks of the volcano at speeds of up to 100 miles per hour. They are dense enough to knock down trees and hot enough to incinerate everything in their path.

Lava flows are produced by many Pavlof eruptions. They are generally not a hazard to humans because they move slowly, their flow path is predictable, and they generally do not travel far from the volcano. For more information on pyroclastic flows, lahars, lava flows and more, please see our article about volcanic hazards.

Pavlof Volcano - 1996 Eruption

Pavlof 1996 eruption: A photo of Pavlof Volcano taken on November 13, 1996. This image shows Pavlof's steep stratovolcano geometry. This eruption began on September 15, 1996 and ended on January 3, 1997. It produced numerous steam and ash eruptions, strombolian eruptions, lava fountains and lava flows. USGS image by Elgin Cook.

Pavlof Topographic Map

Pavlof Topographic Map: USGS topographic map of Pavlof and surrounding volcanic features. Enlarge.

More Information About Pavlof

[1] Pavlof Activity Page: Alaska Volcano Observatory. [2] Pavlof Volcano Summary: Smithsonian Institution, Global Volcanism Program. [3] Preliminary Volcano-Hazard Assessment for the Emmons Lake Volcanic Center, Alaska: United States Geological Survey, Scientific Investigations Report 2006-5248, 2006. [4] Preliminary Volcano-Hazard Assessment for the Emmons Lake Volcanic Center, Alaska: (accompanying maps) United States Geological Survey, Scientific Investigations Report 2006-5248, 2006.

Caldera-Forming Eruptions

Pavlof Volcano gets a lot of attention because it produces a small eruption every few years, making it one of the most active volcanoes in North America. It has the ability to cause temporary air traffic disruptions, but it ranks far below a major threat to local populations and the planet in general.

The eruptive history of the Emmons Lake Volcanic Center includes several large caldera-forming eruptions. Between three and six major caldera-forming eruptions have occurred there in the past 400,000 years. Estimated dates of these major eruptions are around 294,000, 234,000, 123,000, 100,000, 30-50,000, and 26,000 years ago.

Some of these eruptions have been powerful enough to cover up to 1000 square miles with pyroclastic flows of dacite and rhyolite. In some eruptions, they were hot enough to produce welded deposits at distances of up to 20 miles from the vent! Fortunately, these caldera-forming eruptions are extremely rare, and there is no indication that one will occur in the foreseeable future. [3]