AVO reported that on 9 August seismic and infrasound data suggested low-level eruptive activity at Bogoslof; weakly elevated surface temperatures and a minor steam emission were identified in satellite images. No significant activity was observed in cloudy satellite images, and no activity was detected in seismic, infrasound, or lightning data during 10-13 August. Two short pulses of tremor were detected (at 0853, lasting five minutes, and at 0913, lasting three minutes) in seismic data; seismicity returned to baseline levels afterwards. A sequence of seismic events began at 0000 on 15 August; no activity was observed in infrasound, lightning, or satellite data. The Aviation Color Code remained at Orange and the Volcano Alert Level remained at Watch.

Geological Summary. Bogoslof is the emergent summit of a submarine volcano that lies 40 km N of the main Aleutian arc. It rises 1,500 m 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 by exploring expeditions. The present triangular-shaped, 0.75 x 2 km 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. The small Fire Island (New Bogoslof), about 600 m NW of Bogoslof Island, is a remnant of a lava dome formed in 1883.

Source: US Geological Survey Alaska Volcano Observatory (AVO)