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The Alaska Volcano Observatory (AVO) is a joint program of the United States Geological Survey (USGS), the Geophysical Institute of the University of Alaska Fairbanks (UAFGI), and the State of Alaska Division of Geological and Geophysical Surveys (ADGGS).
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Resuspended Volcanic Ash from the Katmai Region to Kodiak Island
Posted: September 04, 2015

Figure 1. View southeast from Overlook Cabin looking over the VTTS. The pyroclastic and ash deposits that fill the valley remain nearly vegetation-free more than 100 years after the 1912 Novarupta-Katmai eruption. Photograph by Game McGimsey, AVO/USGS, June 10, 1991.

Volcanic ash isn’t only a hazard during an eruptive event – in strong winds, loose ash can be picked up and reworked into dust clouds. Resuspension and transport of fine-grained volcanic ash from the Katmai National Park and Preserve region of Alaska has been observed and documented over the past several decades and has likely been occurring ever since the 1912 Novarupta-Katmai eruption. This eruption produced approximately 4 cubic miles (17 cubic kilometers) of ash deposits and 2.6 cubic miles (11 cubic kilometers) of pyroclastic material that filled nearby valleys, creating what is today known as the Valley of Ten Thousand Smokes. Ash in this valley is up to 660 feet (200 meters) thick and the valley remains almost entirely free of vegetation (fig. 1).
During the spring and fall, or whenever strong northwesterly winds blow over the snow-free landscape, the ash can be picked up (reworked) into dust clouds. The ash is especially susceptible to reworking when the ground is very dry. These dust clouds have been observed visually by individuals downwind and also in satellite imagery (figs. 2 and 3). These dust clouds are concentrated between 4,000 and 11,000 feet (1-3.4 kilometers) above sea level and can extend up to 155 miles (250 kilometers) over Shelikof Strait, parts of Kodiak Island, and over the Gulf of Alaska. Trace amounts of ash fallout (typically less than 1/32 inch or 1 mm) have been reported on communities on Kodiak Island. Samples show this fallout is primarily composed of volcanic ash.

Figure 2. MODIS Aqua 1-km resolution true color satellite image shows a resuspended ash cloud generated from high winds scouring the dry, unvegetated deposits in the VTTS. Image obtained November 29, 2010, courtesy of NASA.

What are the hazards associated with resuspended ash?
Clouds of resuspended volcanic ash have not been well studied and little is currently known about the amount or sizes of ash particles in the clouds. Like many other wind-related erosion events in Alaska, strong winds are able to pick up fine material, in this case volcanic ash rather than silt or sand. The clouds are composed of volcanic ash, which is primarily volcanic glass, and they appear similar to ash clouds from a volcanic eruption.
As resuspended ash is physically identical to ash produced in volcanic eruptions, even dilute clouds can pose hazards to human health and aircraft operation. The impact of fallout of resuspended ash is not well known and the largest resuspension events observed so far only produced fallout in trace amounts (less than 1/32 inch or 1 mm). It is not known if this amount presents an air quality issue and thus a public health hazard. The ash does create a hazard to aircraft flying at those elevations. The Alaska Volcano Observatory works closely with the National Weather Service, who has the responsibility to issue forecasts and statements of resuspended volcanic ash More information on volcanic ash is found at: http://volcanoes.usgs.gov/ash/.

Figure 3. Web camera image shows resuspended ash from the Katmai region on September 29, 2014.

How will I know about these events?
Take Home Points

  • These dust clouds are not caused by an active volcanic eruption.

  • These volcanic ash clouds are the result of high winds picking up loose volcanic ash from extensive deposits erupted over 100 years ago from the Novarupta vent on the Alaska Peninsula within Katmai National Park.

  • They can occur regularly in the spring and fall, or whenever strong northwesterly winds blow across the area coincident with extended periods of dry ground surface conditions.

  • Cloud heights have been estimated between 4,000 and 11,000 feet (1 - 3.4 kilometers) above sea level.

  • Clouds can extend up to about 155 miles (250 kilometers) over Shelikof Strait, parts of Kodiak Island and over the Gulf of Alaska.

Get these reports emailed to you: USGS VNS
Friday, October 9, 2015 12:25 PM AKDT (Friday, October 9, 2015 20:25 UTC)

52°49'20" N 169°56'42" W, Summit Elevation 5676 ft (1730 m)
Current Volcano Alert Level: WATCH
Current Aviation Color Code: ORANGE

Nothing significant observed in partly cloudy web camera and satellite views of the volcano over the past week. No significant activity was detected in seismic or infrasound (pressure sensor) data this week.

Cleveland volcano forms the western portion of Chuginadak Island, a remote and uninhabited island in the east central Aleutians. The volcano is located about 75 km (45 mi) west of the community of Nikolski, and 1500 km (940 mi) southwest of Anchorage. The most recent significant period of eruption began in February, 2001 and produced 3 explosive events that generated ash clouds as high as 39,000 ft above sea level. The 2001 eruption also produced a lava flow and hot avalanche that reached the sea. Since then, Cleveland has been intermittently active producing small lava flows, often followed by explosions that generate small ash clouds generally below 20,000 ft above sea level. These explosions also launch debris onto the slopes of the cone producing hot pyroclastic avalanches and lahars that sometimes reach the coastline.

54°45'19" N 163°58'16" W, Summit Elevation 9373 ft (2857 m)
Current Volcano Alert Level: WATCH
Current Aviation Color Code: ORANGE

Seismic activity continues at levels above background and has changed little over the past week. Thermal signals and minor steaming have been observed intermittently in satellite and web camera views of the volcano during the past week. It remains possible that very low level eruptive activity is continuing within the summit crater of the volcano.

Shishaldin volcano, located near the center of Unimak Island in the eastern Aleutian Islands, is a spectacular symmetric cone with a base diameter of approximately 16 km (10 mi). A 200-m-wide (660 ft) funnel-shaped summit crater typically emits a steam plume and occasional small amounts of ash. Shishaldin is one of the most active volcanoes in the Aleutian volcanic arc, with at least 54 episodes of unrest including over 24 confirmed eruptions since 1775. Most eruptions are relatively small, although the April-May 1999 event generated an ash column that reached 45,000 ft above sea level.

56°11'52" N 159°23'35" W, Summit Elevation 8225 ft (2507 m)
Current Volcano Alert Level: ADVISORY
Current Aviation Color Code: YELLOW

Slightly elevated levels of seismicity were detected throughout the past week. Nothing of note was observed in satellite views of the volcano over the past week. Occasional clear web camera images this week showed a small steam plume issuing from the intracaldera cone.

Mount Veniaminof volcano is an andesitic stratovolcano with an ice-filled 10-km diameter summit caldera located on the Alaska Peninsula, 775 km (480 mi) southwest of Anchorage and 35 km (22 mi) north of Perryville. Veniaminof is one of the largest (~300 cubic km; 77 cubic mi) and most active volcanic centers in the Aleutian Arc and has erupted at least 13 times in the past 200 years. Recent significant eruptions of the volcano occurred in 1993-95, 2005, and 2013. These were Strombolian eruptions that produced lava fountains and minor emissions of ash and gas from the main intracaldera cone. During the 1993-95 activity, a small lava flow was extruded, and in 2013, five small lava flows effused from the intracaldera cone over about five months. Minor ash-producing explosions occurred nearly annually between 2002 and 2010. Previous historical eruptions have produced ash plumes that reached 20,000 ft above sea level (1939 and 1956) and ash fallout that blanketed areas within about 40 km (25 mi) of the volcano (1939).


Other Alaska volcanoes show no signs of significant unrest: http://www.avo.alaska.edu/activity/

AVO scientists conduct daily checks of earthquake activity at all seismically-monitored volcanoes, examine web camera and satellite images for evidence of airborne ash and elevated surface temperatures, and consult other monitoring data as needed.

For definitions of Aviation Color Codes and Volcano Alert Levels, see: http://www.avo.alaska.edu/color_codes.php


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John Power, Scientist-in-Charge, USGS
jpower@usgs.gov (907) 786-7497

Jessica Larsen, Acting Coordinating Scientist, UAFGI
jflarsen@alaska.edu (907) 322-4085

The Alaska Volcano Observatory is a cooperative program of the U.S. Geological Survey, the University of Alaska Fairbanks Geophysical Institute, and the Alaska Division of Geological and Geophysical Surveys.



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Page modified: November 15, 2014 16:35
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