Multiple eruptions at Bogoslof, volcanic cloud up to 11 km (36 000 feet) a.s.l.

Multiple eruptions at Bogoslof, volcanic cloud up to 11 km (36 000 feet) a.s.l.

Multiple eruptive bursts were registered at Bogoslof volcano, Alaska starting at 00:49 UTC on June 24, 2017.

The first eruptive burst lasted roughly 10 minutes and was accompanied by strong seismicity, lightning, and infrasound. Thus, the Alaska Volcano Observatory (AVO) raised the Aviation Color Code to RED and Alert level to WARNING.

Satellite data through 01:30 UTC showed a volcanic cloud with an estimated altitude of 11 km (36 000 feet) a.s.l. moving east. It passed over Akutan and the North Pacific Ocean before it was no longer apparent in satellite data. AVO has received no reports of ash fall. This initial event also generated infrasound that was detected by networks on Umnak and Adak Islands. The volcanic cloud also generated several lightning strokes.

The event at 00:49 UTC was followed by five additional eruptive bursts at 03:18 - 03:24 UTC, 04:13 - 04:21 UTC, 05:04 - 05:12 and 05:52 - 05:55 UTC, and 08:40 - 08:44 UTC.

High clouds have moved into the region since the initial explosion, obscuring observations of ash clouds from these later events. The meteorological cloud deck top was at about 8.6 - 9.1 km (28 000 to 30 000 feet) a.s.l., and none of the explosive events has produced a cloud that have risen above it. These explosions were also detected in infrasound data, but no lightning strokes were detected by the World Wide Lightning Location Network (WWLLN).

Bogoslof volcano remains at a heightened state of unrest and in an unpredictable condition. Additional explosions producing high-altitude volcanic clouds could occur at any time. Low-level explosive activity below AVO's ability to detect in data sources may be occurring. These low-level explosions could pose a hazard in the immediate vicinity of the volcano, AVO warns. 

The Aviation Color Code was lowered back to Orange at 19:45 UTC.

Geological summary

Bogoslof is the emergent summit of a submarine volcano that lies 40 km (24.8 miles) north of the main Aleutian arc. It rises 1 500 m (4 920 feet) above the Bering Sea floor. Repeated construction and destruction of lava domes at different locations during historical time has greatly modified the appearance of this "Jack-in-the-Box" volcano and has introduced a confusing nomenclature applied during frequent visits of exploring expeditions.

The present triangular-shaped, 0.75 x 2 km (0.46 x 1.2 miles) island consists of remnants of lava domes emplaced from 1796 to 1992. Castle Rock (Old Bogoslof) is a steep-sided pinnacle that is a remnant of a spine from the 1796 eruption. Fire Island (New Bogoslof), a small island located about 600 m (1 970 feet) NW of Bogoslof Island, is a remnant of a lava dome that was formed in 1883. (GVP)

Featured image: Worldview satellite image of Bogoslof volcano collected at 23:13 UTC on June 12, 2017. The circular embayments were formed by a series of more than 40 explosions that began in mid-December, 2016. These explosions have greatly reshaped the island as material is removed and redeposited as air fall. Vigorous steaming is observed from a region to the south of the most active vent areas in the lagoon. Lava extrusion produced a circular dome that first rose above the water on June 5 and grew to a diameter of ~160 m (525 feet) before being destroyed by an explosion early in the day on June 10. Large blocks of the destroyed dome can be seen littering the surface of the island near the lagoon.


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