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A little more than 110 years ago, the remote wilderness of the Alaska Peninsula experienced what probably the largest, more explosive eruption of the 20th century. This eruption covered the area with tens of meters of volcanic ash and debris, creating the aptly named The Valley of 10,000 Smokes. Many volcanoes do not eEven today, when winds pick up in late summer and fall, ash from this eruption can be elevated and raised high in the air, sometimes even making people think an eruption has started.

The strange thing about the 1912 explosion is that it came from a volcano that wasn’t even on the map before the eruption. Not only that, but also volcanoes that they weren’t even the source of all that volcanic material that fell apart during the eruption. Katmai saw a ~1.6 by 2.3 mile caldera formation in June 1912, although the eruption itself it was coming from what would be called Novarupta just to the west. If you want to read all about those fateful days in Alaska, I wrote about it during the 100th anniversary.

What has happened since 1912

Trident Volcano and its neighbors (marked). Credit: Alaska Volcano Observatory, Matt Lowen.

From the volcanoes in the vicinity of Novarupta (Katmai, Griggs, Magick, Martin and Trident), only two have erupted since 1912. The most distant of the group, Martin, had two minor eruptions in 1951 and 1953. Tridentthe volcano closest to Novarupta’s action saw 14 eruptions between 1949 and 1974. Some of them were of relatively good size, reaching VEI 3. Since then, however, it has been silent.

Lightning fast forward to August 2022. Since then, volcanologists at the Alaska Volcano Observatory have noticed earthquakes coming in swarms under the Trident. Last summer, earthquakes were numerous, but they started relatively deep, focused about 16 miles below the volcano. Over the course of several days, these earthquakes became shallower and shallower, reaching the surface 3 miles away.

Since early January, earthquakes have remained at about this depth, with dozens of earthquakes each week. Not only that, but there were earthquakes under the nearby volcanoes Martin and Mageik. Things are definitely in a state of excitement in the Novarupta-Katmai area.

Earthquakes in the Trident region since 2003. The sharp jump from the summer of 2022 is evident on the right. Credit: Alaska Volcano Observatory, Aaron Wech.

On February 22, the frequency of earthquakes below Trident jumped, so the Alaska Volcano Observatory raised the alert to Yellow (the second of four warnings). This was mostly to give people enough time to think about what might happen if Trident or one of the other volcanoes erupts again.

What’s happening at Trident?

Current evidence does not seem to point to an eruption in the near future, but whenever volcanologists see (1) an increase in earthquakes under a volcano, (2) these earthquakes lasting months and (3) the depth of the earthquakes decreases over time, then they know it’s time to start watching closely. This is because this pattern is likely caused by magma rising from deep in the crust up into the volcano’s shallow magma system. In a way, the volcano is preparing for… something.

Now, whether something was then a new eruption or just magma replenishment without an explosion is unknown at this point. Volcanologists would like more signs, such as deformation of the volcano or increased gas emissions or an even more intense swarm of earthquakes. None of this has yet happened in Trident.

If Trident erupts, we’re probably not talking about another huge eruption like the Novarupta explosion in 1912. When Trident was busy erupting in the 1940s-70s, most of its activity was moderate explosions that sent ash up 30,000 feet with accompanying lava and pyroclastic flows. Fortunately, in such a remote location, the greatest danger to aircraft is from all the potential ash.

So Trident joined Great Sitkin, Aniakchak, Semisopochnoi and Takawangha on high alert through the Aleutian Volcanoes of Alaska. It wouldn’t be shocking for something new to happen at Trident, especially after almost 50 years of silence. The question will be whether these current disturbances are a harbinger of further eruptions.

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