While the main goal of this cruise is to image the Aleutian-Alaska Subduction Zone (AASZ) to understand the generation of large earthquakes, a perk is viewing the truly awesome volcanoes that form the Aleutian Arc. That is…if we could see them! Every time we have gotten close enough to view the volcanoes along the Alaskan Peninsula, the skies have been blanketed in a thick cover of fog. As the lone volcano scientist on this expedition, I have been holding out hope that maybe one of these days I will be able to gaze upon some of the glorious edifices. Still, there are a few days left of this expedition. Maybe our luck will change!
Figure 1 : Searching the fog for volcanoes
The 4000 kilometer long Aleutian Arc—reaching from the Kamchatka Peninsula to the west to mainland Alaska to the east—is one of Earth’s most active volcanic arc, hosting approximately 142 volcanoes and volcanic fields that have been active in the last two million years (Figure 21). Out of those 142 volcanoes, 94 have been active within the last 10,000 years and 50 active in the last 260 years2.
Figure 2: Map of Historically Active Volcanoes in Alaska1. During parts of our voyage we have been close enough to scan the horizon for Aniakchak and Chiginagak volcanoes, and tomorrow we hope to catch a glimpse of Veniaminof volcano.
This arc has produced an extensive variety of eruption styles, ranging from continuous lava fountaining (Hawaiian-type eruptions) to intervallic bursts of lava flows and tephra (Strombolian-type eruptions) to even large volume, highly explosive (Plinian eruptions) type eruptions that lead to caldera collapse. While these caldera forming eruptions are rare along the arc, 14 of the volcanic systems have produced them, and, remarkably, 11 of them are located along the Alaskan Peninsula. The reason for this increased flux of magma in the region is still not understood.
Recently, Mount Veniaminof, one of the peninsula stratovolcano with a caldera, erupted from September 4, 2018 until January, 2019 and sustained volcanic unrest (i.e. seismic activity caused by the movement of magma and other fluids through the Earth’s crust) until a few months ago. While the eruption was not large, there was some distribution of volcanic ash. One of the main hazards that the Alaskan Volcano Observatory (https://avo.alaska.edu/) monitors is the dispersal of ash in the atmosphere during an eruption because it poses a considerable threat to nearby towns and passenger and freight aircrafts. Transpacific flights frequently cross over the Alaskan Peninsula, and, in 1989, an aircraft crashed due to an eruption at Redoubt. Moreover, Ted Stevens International Airport in Anchorage is one of the main air cargo ports in the United States. Therefore, monitoring these volcanoes is critical for hazard mitigation.
Figure 3: Land! Some of the peaks are old stratovolcanoes that were active during the Holocene
Edit: The day has come! Volcanoes have been spotted!
University of Nevada, Reno
1Cameron, C.E., Schaefer, J.R., and Mulliken, K.M., 2018, Historically active volcanoes of Alaska: Alaska Division of Geological & Geophysical Surveys Miscellaneous Publication 133 v. 3, 2 sheets. http://doi.org/10.14509/30142 2Buurman, H., Nye, C.J., West, M.E., Cameron, C., 2014. Regional controls on volcano seismicity along the Aleutian arc. Geochem. Geophys. Geosyst. 15 (4), 1147–1163.