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Volcanic Hazards in Alaska's National Parks: Ash, Lahars, Gas and Who Watches
During Redoubt Volcano's 1989-1990 eruption, a 747-400 flew into its ash cloud near Anchorage and temporarily lost power in all four engines. It landed safely but incurred $80 million in damages. The incident led to the expansion of the Alaska Volcano Observatory (AVO) and remains an example of the need for vigorous volcano monitoring and hazard communication. This overview by Katherine Mulliken, Kristi Wallace, Cheryl Cameron and Chris Waythomas of AVO appeared in Alaska Park Science.
Shishaldin Volcano with Isanotski Peaks behind it, August 15, 2018. Photo courtesy of Matt Loewen, USGS/AVO.
The volcanoes
Alaska has over 100 volcanoes, 54 of them considered historically active. A volcano counts as historically active if it meets any one of four tests: a documented or strongly suspected eruption since 1700, persistent fumaroles near boiling point, significant deformation with a volcanic cause, or an earthquake swarm with a volcanic cause. Alaska's national parks, preserves and monuments hold 14, with seven confirmed eruptions among them in the past 100 years.
| Park | Historically active volcanoes |
|---|---|
| Aniakchak National Monument and Preserve | Aniakchak Crater |
| Katmai National Park and Preserve | Mount Douglas, Fourpeaked Mountain, Kukak Volcano, Snowy Mountain, Mount Griggs, Mount Mageik, Mount Martin, Trident Volcano, Novarupta and Mount Katmai |
| Lake Clark National Park and Preserve | Iliamna Volcano and Redoubt Volcano, both National Natural Landmarks |
| Wrangell-St. Elias National Park and Preserve | Mount Wrangell |
How they are watched
AVO studies past eruptions and publishes research, geologic maps and hazard assessments. It monitors volcanoes with seismometers, GPS stations, web cameras and infrasound sensors that send real-time data, along with daily review of satellite images and overflights to measure gas, and newer tools such as lightning detection, which can reveal volcanic plumes. Its seismic network has 212 stations in 34 networks. AVO can confirm "non-eruptions" after false reports, especially about Mount Wrangell and Iliamna.
The U.S. uses a standard volcano alert system: an Alert Level and an Aviation Color Code for each monitored volcano. Changes, such as an earthquake swarm, are announced on the AVO website, social media, news outlets and the Volcanic Activity Notification Service. AVO's job is to detect unrest and report potential hazards. The Federal Aviation Administration, National Weather Service and Alaska's emergency management division also have reporting duties, spelled out in an interagency operating plan for volcanic ash.
Distant hazards: ash
Because many volcanoes are remote, the hazards of greatest concern are those that reach far away, mainly drifting ash clouds and ashfall. Ash clouds form when an explosive eruption shatters magma and injects fine particles high into the air within an hour, sometimes 10 to 20 km above the volcano. The ash is abrasive and can severely damage aircraft, eroding engine and electrical parts and scouring windows, wings and landing gear. Many visitors reach the parks in small aircraft flying at 10,000 to 20,000 feet, where ash is most likely, so summer ash emissions could sharply limit access.
Ashfall differs by distance: bigger particles settle near the vent and smaller ones travel farther. Trace ashfall, less than 1/32 of an inch, is common far away and causes eye and breathing irritation. More can harm plants and animals, and wet ash is much denser than dry, so heavy accumulation can collapse buildings, block roads, foul water and disrupt communication.
- The 1912 Novarupta-Katmai eruption, the most voluminous of the 20th century, still causes seasonal hazard when high winds and dry conditions lift its ash again.
- The 1931 Aniakchak eruption left millimeters of ash as far as Kodiak Island.
- During Redoubt's 1989-1990 eruption several jetliners met the ash cloud, one as far away as Texas.
Near hazards
Hazards within about 19 miles (30 km) of a vent include:
| Hazard | What it is | Alaska example |
|---|---|---|
| Ballistics | Pebble- to boulder-sized bombs thrown out explosively, usually landing within a few kilometers | |
| Lahars | Flows of water, rock and mud with the consistency of wet concrete that can travel many tens of kilometers; in Alaska they typically come when hot debris meets ice and snow | In Redoubt's 2009 eruption lahars ran more than 25 miles (40 km) down the Drift River valley and flooded parts of the Drift River Oil Terminal, forcing evacuation and an end to operations |
| Pyroclastic flows and surges | Hot, turbulent mixtures of gas and rock that may travel more than 19 miles (30 km) | Katmai-Novarupta in 1912 sent about 2.6 cubic miles (11 cubic kilometers) into nearby valleys, now the Valley of Ten Thousand Smokes |
| Lava flows and domes | Alaska's flows are usually slow and avoidable, but a collapsing dome can produce block-and-ash flows, and lava over snow can make ground unstable | Veniaminof's 2013 eruption sent lava over glacier ice in its caldera |
| Rockfalls, landslides, debris avalanches | Unstable, poorly consolidated volcanic rock; large landslides can be set off by tectonic earthquakes | Small slides at Iliamna, and rock-ice-snow avalanches on Redoubt's upper cone |
| Gases | Water vapor, carbon dioxide, sulfur dioxide, hydrogen sulfide, hydrogen and fluorine can irritate eyes and lungs; carbon dioxide is heavier than air and can pool in low places | Fourpeaked Mountain was not considered historically active until 2006, when steam explosions and sulfur emissions began near its summit |
Gas is usually not a danger in the parks because vents often lack terrain that traps it and wind disperses it, but crater floors and flank fumaroles can collect gas and should be avoided. In Wrangell-St. Elias National Park and Preserve near Glennallen, carbon dioxide-charged warm saline water reaches the surface at two groups of mud volcanoes, called Tolsona and Klawasi, where visitors can be exposed too.
Aerial view of Redoubt Volcano's north flank on April 4, 2009: pyroclastic debris that came down the Drift glacier gorge flowed over the crevassed ice. Photo by K.F. Bull, courtesy of AVO/USGS.
Fumarole on Fourpeaked Mountain, February 22, 2007. Sulfur emission from the vent stains the snow yellow. Photo by Cyrus Read, courtesy of AVO/USGS.
What visitors can do
AVO relies on the National Park Service to maintain monitoring stations, do geologic work and respond to eruptions. The authors recommend that park staff and visitors learn the volcano alert system, subscribe to the Volcanic Activity Notification service and check the Alert Level and Aviation Color Code of nearby volcanoes.
Sources
- Katherine Mulliken, Kristi Wallace, Cheryl Cameron and Chris Waythomas, Alaska Volcano Observatory, Volcanic Hazards in Alaska's National Parks, Alaska Park Science 18(1), National Park Service; rewritten in hubnx's own words.