Hazard Notification System (HANS) for Volcanoes


U.S. Geological Survey
Wednesday, September 14, 2022, 9:16 AM AKDT (Wednesday, September 14, 2022, 17:16 UTC)

58°14'3" N 155°6'9" W, Summit Elevation 3599 ft (1097 m)
Current Volcano Alert Level: NORMAL
Current Aviation Color Code: GREEN

A swarm of earthquakes beneath Trident volcano began on August 24, 2022 and is ongoing but now at a decreased rate. Earthquake depths at the beginning of the swarm were mostly deep, around 25 km (16 miles) below sea level, and became progressively shallower to around 5 km (3 miles) by August 28. Since August 28, most earthquakes have been at depths of 0 to 7 km (0 to 4.3 miles) below sea level. Earthquake magnitudes (M) have ranged from M –0.7 to M 1.9. At the peak of the swarm, dozens of earthquakes were occurring daily beneath the volcano, and over the past week earthquake rates have decreased to just a few per day. A few episodes of weak seismic tremor and low frequency earthquakes have also occurred. No other signs of unrest have been detected in available monitoring data.  

The increase in seismic activity is likely caused by movement of magma or magmatic fluids. Increases in seismic activity have been detected previously at Trident and other similar volcanoes, with no subsequent eruptions. We expect additional shallow seismicity and other signs of unrest, such as gas emissions, elevated surface temperatures, and surface deformation to precede any future eruption, if one were to occur.  

Should activity increase, AVO will issue further notices and possibly increase the Aviation Color Code and Volcano Alert Level.
AVO monitors Trident with a local network of seismometers, a webcam, remote sensing data, and regional infrasound and lightning networks. To view current monitoring data, see https://avo.alaska.edu/activity/Trident.php

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 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 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 148 km (92 miles) southeast of King Salmon and 440 km (273 miles) southwest of Anchorage.


Information on all Alaska volcanoes is available at: http://www.avo.alaska.edu.

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

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Michelle Coombs, Scientist-in-Charge, USGS, mcoombs@usgs.gov, (907) 786-7497

Jessica Larsen, Acting Coordinating Scientist, UAFGI, jflarsen@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.