Tanaga Island Hides a History of Fire in a Blanket of Fog

Tanaga Island is a tiny patch of beauty, fire, and rock stranded in the Bering Sea. The picturesque island is a hidden gem of black rocks, dramatic waterfalls, velvety moss, and tendrils of fog in these fieldwork photographs from the U.S. Geological Survey.

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Tanaga in 2012. Image credit: Roger Clifford/AVO/USGS

A history of rock and fire is revealed in beautiful photographs of Tanaga Island by a U.S. Geological Survey scientists from their field seasons. The island is part of the Aleutian Island chain in Alaska.

Rounded cobbles along the beaches of Tanaga Island. Image credit: ML Coombs/AVO/USGS

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Tanaga is home to a complex of stratovolcanoes that slowly built up the island in layers of eruptions. Thick cliffs bare columnar basalts, a relic of ancient lava flows. The hexagonal columns are formed by cracks sprouting perpendicular to the cooling surface.

The island is pretty much the definition of “in the middle of no where.” It’s 100 kilometers (62 miles) west of Adak Island, the nearest inhabited location. But it isn’t untouched: along with official monitoring stations to track eruptions, the island is home to an emergency landing strip and pier for the Navy, and several seasonally-inhabited cabins.

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Researcher near solar-powered monitoring station for Tanaga volcano. Image credit: Tim Plucinski/AVO/USGS

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The tallest trio of peaks are Tanaga volcano at 1,806 meters (5,925 feet) above sealevel, Takawagha at 1,449 meters (4,754 feet), and Sajaka 1,354 meters (4,443 feet). Layers of thick mist speak to the heavy rain that feeds streams to cut steep waterfalls. That water creates a smothering blanket of lush vegetation, softening the sharp rugged terrain.

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Waterfalls along the north side of Tanaga Island. Image credit: John Lyons/AVO/USGS

All this beauty hides a sharp bite: this island is built on a history of violent eruptions.

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Fieldwork on the rugged terrain at the remote island requires helicopter time. Image credit: Tim Plucinski/AVO/USGS

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The most recent eruption was in 1914, with possible eruptions from 1763 to 1770, 1791, and in 1829. All eruptions were probably from the summit vent of Tanaga, and from another vent 1,584 meters (5,197 feet) on the northeastern flank; Takawangha has a quartet of craters marking eruptions within the past few thousand years.

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Researcher John Lyons replacing a broken solar panel at the Tanaga volcano monitoring station TANE during the 2015 summer field season. Image credit: Mattia Pistone/AVO/USGS

Formed along a subduction boundary, stratovolcanos erupt a intermediate lavas with a moderate silica content: the eruptions are usually fairly violent, producing clouds of ash and blocky debris.

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You can check the latest activity reports from Tanaga volcano at the Alaska Volcano Observatory.

Top image: Tanaga Island, Alaska in August 2015. Credit: Michelle Coombs/AVO/USGS


Contact the author at mika.mckinnon@io9.com or follow her at @MikaMcKinnon.

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