USGS Volcano Notice - DOI-USGS-AVO-2024-01-05T09:28:37-09:00

ALASKA VOLCANO OBSERVATORY WEEKLY UPDATE
U.S. Geological Survey
Friday, January 5, 2024, 12:52 PM AKST (Friday, January 5, 2024, 21:52 UTC)

GREAT SITKIN (VNUM #311120)
52°4'35" N 176°6'39" W, Summit Elevation 5709 ft (1740 m)
Current Volcano Alert Level: WATCH
Current Aviation Color Code: ORANGE

Slow eruption of lava within the summit crater of Great Sitkin Volcano continued over the last week. Satellite radar images showed continued growth of the lava flow field to the east. Radial cracks opening around the central vent area pushed material near the vent north more than 50 ft (15 m). Only minor earthquake activity was noted until January 2 when a storm-related power failure took local monitoring data offline.

The prolonged period of lava eruption at Great Sitkin Volcano began in July 2021. No explosive events have occurred since a single event in May 2021.

The volcano is monitored by local seismic, geodetic, and infrasound sensors, web cameras, regional infrasound and lightning networks, and satellite data.

Great Sitkin Volcano is a basaltic andesite volcano that occupies most of the northern half of Great Sitkin Island, a member of the Andreanof Islands group in the central Aleutian Islands. It is located 26 miles (43 km) east of the community of Adak. The volcano is a composite structure consisting of an older dissected volcano and a younger parasitic cone with a ~1 mile (1.5 km)-diameter summit crater. A steep-sided lava dome, emplaced during the 1974 eruption, occupies the center of the crater. That eruption produced at least one ash cloud that likely exceeded an altitude of 25,000 ft (7.6 km) above sea level. A poorly documented eruption occurred in 1945, also producing a lava dome that was partially destroyed in the 1974 eruption. Within the past 280 years a large explosive eruption produced pyroclastic flows that partially filled the Glacier Creek valley on the southwest flank.

SHISHALDIN (VNUM #311360)
54°45'19" N 163°58'16" W, Summit Elevation 9373 ft (2857 m)
Current Volcano Alert Level: ADVISORY
Current Aviation Color Code: YELLOW

Low-level unrest continued at Shishaldin Volcano over the past week. Frequent, small, low-frequency earthquakes were noted in seismic data, but explosion signals were largely absent, and the Aviation Color Code and the Volcano Alert Level were lowered to YELLOW/ADVISORY on January 2. Ongoing minor activity is likely occurring deep within the vent and not causing any changes visible at the surface in satellite or web camera data. Minor steam emissions were observed during clear weather in web camera images on January 1. No sulfur dioxide emissions or thermal anomalies were detected in satellite data.

Thirteen significant explosive events have taken place at Shishaldin since July 12, 2023. These events have been preceded by increases in seismicity in the hours to days before they occur. It is unknown how long this period of ongoing activity will last. However, previous eruptions of Shishaldin Volcano have lasted weeks to months with repeated cycles of eruptive activity like those seen since July.

Local seismic and infrasound sensors, web cameras, and a geodetic network monitor Shishaldin Volcano. In addition to the local monitoring network, AVO uses nearby geophysical networks, regional infrasound and lightning data, and satellite observations to detect eruptions.

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 10 miles (16 km). A 660 ft wide (200 m) 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 28 confirmed eruptions since 1824. Most eruptions are relatively small, although the April-May 1999 event generated an ash column that reached 45,000 ft. (14 km) above sea level.

KANAGA (VNUM #311110)
51°55'27" N 177°9'44" W, Summit Elevation 4288 ft (1307 m)
Current Volcano Alert Level: ADVISORY
Current Aviation Color Code: YELLOW

Small earthquakes were detected at Kanaga Volcano until January 2 when a storm-related power failure took local monitoring data offline. Satellite and web camera images throughout the week were obscured by clouds and no new eruptive activity was seen.

Satellite radar images show evidence for large northwest-southeast oriented fractures intersecting the summit crater which likely formed around the December 18 (December 19 UTC) explosive event. These cracks appear similar to one formed in 2012. An annotated radar image is available at http://www.avo.alaska.edu/images/image.php?id=195260.

This new unrest indicates a possibility for sudden explosions to occur at any time. These explosions may produce ash clouds exceeding 20,000 feet above sea level. Prior to the current activity, the last unrest at Kanaga Volcano was in February 2012 when a steam-driven explosion occurred together with the opening of a large fissure on the southern crater rim.

Kanaga Volcano is monitored by local seismic and infrasound sensors, regional infrasound and lightning networks, and satellite data.

Kanaga Volcano occupies the northern corner of Kanaga Island, one of the most southerly members of the central Aleutian chain. It is a symmetric composite cone 4288 ft (1307 m) high and 3 miles (4.8 km) in diameter at sea level, built of interbedded basaltic and andesitic lava flows, scoria layers, and pyroclastic rocks. Kanaga Volcano’s last significant eruption was in 1994–1995. At least two significant ash plumes were recorded over the course of this eruption: the first, to ~25,000 ft (7.5 km), occurred on February 21, 1995 and the second on August 18, 1995, when an eruption cloud reached ~15,000 ft. (4.5 km). A light dusting of ash fell on the community of Adak and air traffic was disrupted due to continuing low-level activity and cloudy conditions which prevented visual approaches to the Adak air field.

TRIDENT (VNUM #312160)
58°14'3" N 155°6'9" W, Summit Elevation 3599 ft (1097 m)
Current Volcano Alert Level: ADVISORY
Current Aviation Color Code: YELLOW

Earthquake activity in the vicinity of Trident Volcano remained slightly elevated over the past week. Seismic activity in the Katmai region is typically higher than other places in the arc, and current activity is near long-term background levels. No volcanic activity was observed in satellite and web camera views of the volcano.

The current period of unrest began in August 2022. Since then, most earthquakes have occurred within the shallow crust, with depths less than 4 miles (6 km) below sea level; however, deeper quakes (greater than 9 miles or 15 km depth) have been notable during much of the unrest period. Surface uplift, low-frequency earthquakes, and seismic tremor – all consistent with magmatic activity – have been observed over this extended period as well.

Increases in seismic activity have been detected previously at Trident Volcano and other similar volcanoes and did not result in eruptions. We expect additional shallow seismicity and other signs of unrest, such as gas emissions, elevated surface temperatures, and ground uplift, to precede any future eruption if one were to occur.

Trident Volcano is monitored by local seismic sensors, web cameras, regional infrasound and lightning networks, and satellite data.

Trident is one of the Katmai group of volcanoes located within Katmai National Park and Preserve on the Alaska Peninsula. Trident consists of a complex of four cones and numerous lava domes, all andesite and dacite in composition, that reach as high as 6,115 ft (1,864 m) above sea level. An eruption beginning in 1953 constructed the newest cone, Southwest Trident, and four lava flows on the flank of the older complex. This eruption continued through 1974 and produced ash (an initial plume rose to 30,000 ft or 9 km above sea level), bombs, and lava at various times. Fumaroles remain active on the summit of Southwest Trident and on the southeast flank of the oldest, central cone. Trident is located 92 miles (148 km) southeast of King Salmon and 273 miles (440 km) southwest of Anchorage.

CONTACT INFORMATION:

Aaron Wech, Acting Scientist-in-Charge, USGS awech@usgs.gov (907) 786-7497

David Fee, Coordinating Scientist, UAFGI dfee1@alaska.edu (907) 378-5460

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.