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The Global Volcanism Program has no activity reports for Bogoslof.
The Global Volcanism Program has no Weekly Reports available for Bogoslof.
Reports are organized chronologically and indexed below by Month/Year (Publication Volume:Number), and include a one-line summary. Click on the index link or scroll down to read the reports.
06/1992 (BGVN 17:06) Steam and ash emission
07/1992 (BGVN 17:07) New lava dome enlarges island
06/1992 (BGVN 17:06) Steam and ash emission
A eruption . . . had begun by 6 July, when airplane pilots first reported steam and ash rising through low clouds. Similar activity was seen through the week, when satellite images revealed repeated plumes from Bogoslof. Pilots reported a cloud to ~3 km altitude on 14 July at 1815. Satellite images showed the plume extending roughly 100 km SE, to the S side of Unalaska Island. An image from 16 July at 1140 showed another plume extending ~100 km E to Unalaska. That day, a pilot saw a white plume rising to ~4 km altitude. An episode of vigorous steam and ash ejection began on 20 July at about 1700, and material had reached nearly 8 km asl by 1725, drifting NNE. A dark gray cloud that was ~15 km wide at 3 km altitude was moving NW from the volcano several hours later. Poor weather prevented subsequent observations, but satellite images showed no volcanic plumes rising above weather-cloud tops at ~6 km elevation. There have been no reports of ashfall. Cloudy weather has prevented direct observation of the island . . . .
Information Contacts: AVO; SAB.
07/1992 (BGVN 17:07) New lava dome enlarges island
A large new lava dome grew on the N side of Bogoslof Island (figure 1) during the steam-and-ash eruption reported in 17:6. The eruption apparently began about 6 July, and the last reports of activity were received on 24 July.
|Figure 1. Sketch map of Bogoslof Island, showing the 1992 dome and new flat land just offshore (labeled "rocks"). Pre-1992 features are drawn from a 1982 pocket-transit survey by John Reeder, which had shown substantial erosion of the soft 1926-27 pyroclastic deposits since USGS mapping in 1947 (Byers, 1959). Courtesy of John Reeder.|
A plume was first visible on satellite imagery at about 1500 on 6 July, rising to an estimated 3 km altitude. Previous small plumes, if any, would have been obscured by clouds at about 6 km altitude that had remained over the area for the previous few days. Just after 1700 on 6 July, Thomas Madsen (Aleutian Air) saw a continuously rising steam column that disappeared into low clouds at 350 m altitude. From his vantage point 30 km SSE, the column appeared to be emerging from the sea just beyond the island. No eruptive activity had been evident during his previous flight two days earlier. At about 1800, Joe May and David Alborn (MarkAir) saw a white plume reaching at least 1.8 km altitude. During the late afternoon of 7 July, a commercial fisherman saw a rocky new island, with steam and some ash emerging from its summit, between Bogoslof Island and Fire Island (the 1883 dome). A fracture extended from the new island's summit to the sea, from where steam was also rising. No eruptive activity had been evident when the fisherman passed Bogoslof early 6 July.
Only intermittent small plumes appeared on satellite imagery through 13 July. However, plumes were continuous for the next two days, reaching a maximum altitude, on 14 July, of 5.5 km. The largest plume, at 1140 on 15 July, extended ~100 km ESE over neighboring Unalaska Island at 3-3.5 km altitude. At 1755 that day, May and Alborn saw a fairly dark, continuous, steam-and-ash plume that reached about 3.5 km elevation. Satellite images again showed only intermittent plumes 16-17 July, and none since then. Additional pilot observations included a rapidly rising mushroom-shaped cloud with a black stem, reaching at least 4.5 km above sea level on 17 July at 1623 (Wyman Owens, Peninsula Airways). On 20 July at 1830 Joseph Maricelli (Northwest Airlines) saw a gray plume rising from Bogoslof, with a very pale top that may have reached 8 km altitude. A gray cloud was still rising to 4.5 km when Randy Lovett and Tom Peebles (MarkAir) passed at 2056.
Photographs taken from a boat by Larry Shaishnikoff on 21 July, and video footage from a U.S. Coast Guard C-130 aircraft on 24 July, show a profusely steaming new lava dome at the N tip of the main island. Steam with some ash was emerging from most of the dome's surface during Shaishnikoff's visit. Incandescent lava could be seen within large crags over most of the dome, but was brightest on the upper NW and SE flanks. Estimates of its size from the video footage (AVO) and photographs (John Reeder) were similar, at ~80-90 m high and roughly 300-400 m across. It has a steep-sided central spire surrounded by a blocky, more gently sloping debris apron, and is adjacent to the remnant of the 1927 dome. Rock color and surface texture looked very similar to those of the 1927 dome in the Shaishnikoff photos. Approximately horizontal new land ("rocks" on figure 1) extended slightly above sea level just NNE of the dome. No steaming was occurring from these rocks, which may have been uplifted sea floor. Dall porpoises, numerous birds, and some Steller sea lions near Fire Island, several hundred meters from the new dome, did not appear to have been affected by the activity.
Pilot reports of steaming and possible ash emission continued through 24 July, after which occasional pilot observations indicated no further significant activity.
No ashfall has been reported at the two nearest towns, Dutch Harbor/Unalaska (100 km E of Bogoslof) and Nikolski (Umnak I., 120 km SW). The principal hazards from Bogoslof's eruptions are to aircraft in the Aleutian Islands and on Trans-Pacific international routes across the Bering Sea. No aircraft incidents have been reported. A SIGMET issued 20 July was cancelled the next day. No seismometers are maintained near the island.
The volcano's subaerial portion consists of fragmental deposits, agglomerate, lava spires, dome remnants, and beach sediments, all of historical age (Byers, 1959). All sampled rocks are high-potassium andesites and basalts (Arculus et al., 1977). The island is remote and uninhabited, but houses a large sea-lion rookery. The island's low elevation and frequent explosive activity since the first historical eruption in 1796 have resulted in rapid, well-documented morphologic changes over the past 200 years. Particularly vigorous eruptions occurred in 1883, 1907 (both of which deposited small amounts of ash on Dutch Harbor), and 1926-27. These eruptions were characterized by sporadic, violent explosions, with lava flows and dome-building continuing for several months (Jaggar, 1930). Three kilometers of muddy water encountered by a ship near the island in September 1951 may have been from a submarine eruption.
References. Arculus, R., Delong, S., Kay, R.W., Brooks, C., and Sun, S., 1977, The Alkalic Rock Suite of Bogoslof Island, Eastern Aleutian Arc, Alaska: Journal of Geology, v. 85, p. 177-186.
Byers, F.M., 1959, Geology of Umnak and Bogoslof Islands, Alaska: USGS Bulletin 1028-L.
Jaggar, T., 1930, Recent Activity of Bogoslof Volcano: The Volcano Letter, no. 275, p. 1-3.
Information Contacts: AVO; J. Reeder, ADGGS.
Bogoslof is the emergent summit of a submarine volcano that lies 40 km north of the main Aleutian arc. It rises 1500 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 of 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. Fire Island (New Bogoslof), a small island located about 600 m NW of Bogoslof Island, is a remnant of a lava dome that was formed in 1883.
Summary of Holocene eruption dates and Volcanic Explosivity Indices (VEI).
|Start Date||Stop Date||Eruption Certainty||VEI||Evidence||Activity Area or Unit|
|1992 Jul 6||1992 Jul 24||Confirmed||3||Historical Observations||North tip of island (NE of 1927 dome)|
|[ 1951 Sep 21 ]||[ Unknown ]||Uncertain||0|
|1931 Oct 31||Unknown||Confirmed||1||Historical Observations||1926-1927 dome|
|1926 Jul||1928||Confirmed||2||Historical Observations||Between New and Old Bogoslof|
|[ 1913 Jul ]||[ Unknown ]||Uncertain||Tahoma Peak|
|1909 Sep||1910 Sep 19||Confirmed||2||Historical Observations||Tahoma Peak|
|[ 1908 Jan 15 ± 45 days ]||[ Unknown ]||Uncertain||Metcalf Peak|
|1906 Mar 1 ± 30 days||1907 Sep 1||Confirmed||3||Historical Observations||Metcalf Peak, McCullough Peak|
|1883 Sep 27 (in or before)||1895 ± 2 years||Confirmed||3||Historical Observations||New Bogoslof (Grewingk)|
|1806||1823||Confirmed||2||Historical Observations||Old Bogoslof (Castle Rock)|
|1796 May||1804||Confirmed||3||Historical Observations||Old Bogoslof (Castle Rock)|
This compilation of synonyms and subsidiary features may not be comprehensive. Features are organized into four major categories: Cones, Craters, Domes, and Thermal Features. Synonyms of features appear indented below the primary name. In some cases additional feature type, elevation, or location details are provided.
|Feature Name||Feature Type||Elevation||Latitude||Longitude|
|Mcculloch Peak||Former dome|
|Metcalf Domes||Former dome|
|Ship Rock||Former dome|
|Tahoma Peak||Former dome|
|Steam clouds produced by degassing of a growing lava dome rise from the northern tip of Bogoslof Island on July 21, 1992. The 1992 eruption was first observed on July 6, when pilots saw steam and ash rising from low clouds above the volcano. On July 20 an ash column rose to 8 km. A new lava dome grew to 100-m height by the time the eruption ended in late July. The low, 1927 basaltic lava dome forms the dark mass to the right with the pinnacle of Castle Rock behind it.
Photo by Larry Shaishnikoff, 1992 (courtesy of John Reeder, Alaska Div. Geology & Geophysical Surveys).
|Lava dome remnants from three historical eruptions can be seen in this NW-looking aerial view of Bogoslof Island in the Aleutians. The pinnacle on the left is Castle Rock, also referred to as Old Bogoslof, a remnant of a 1796 lava dome. The circular, flat-topped area to its right is a remnant of a 1927 lava dome. The most recent eruption of Bososlof, in 1992, produced the light-colored conical lava dome forming the tip of the island at upper right. Frequent eruptions and vigorous wave erosion have greatly modified the island in historical time.
Photo by Chris Nye, 1994 (Alaska Division of Geological & Geophysical Surveys).
|An aerial view shows the 1992 lava dome of Bogoslof Island, the summit of a largely submarine stratovolcano located in the Bering Sea 50 km behind the main Aleutian arc. The 1992 lava dome grew to a height of 100 m in July at the northern tip of Bogoslof Island. The island is about 1.5 x 0.6 km wide, and due to its frequent eruptive activity and energetic wave action, has changed shape dramatically since first mapped in the late 1700's.
Photo by Tom Miller, 1994 (Alaska Volcano Observatory, U.S. Geological Survey).
|Bogoslof Island is the summit of a largely submarine stratovolcano located in the Bering Sea 50 km behind the main Aleutian arc. The island is about 1.5 x 0.6 km wide, and due to its frequent eruptive activity and energetic wave action, has changed shape dramatically since first mapped in the late 1700's. The conical, rubbly lava dome and offshore spire at the northern tip of the island (bottom center) were formed in 1992. The circular, flat area at the right is a remnant of the 1927 lava dome, and the steep pinnacle is Castle Rock, a 1796 dome remnant.
Photo by Terry Keith, 1994 (Alaska Volcano Observatory, U.S. Geological Survey).
|Lava dome remnants from four historical eruptions can be seen in this NW-looking aerial view of Bogoslof Island in the Aleutians. The pinnacle on the left is Castle Rock, also referred to as Old Bogoslof, a remnant of a 1796 lava dome. The circular, flat-topped area to its right is a remnant of a 1927 lava dome. The most recent eruption of Bososlof, in 1992, produced the light-colored conical lava dome forming the tip of the island at upper right part of the island. The island at the upper right was formed in 1883.
Photo by John Sease, 1998 (NMS/NOAA).
The following references have all been used during the compilation of data for this volcano, it is not a comprehensive bibliography. Discussion of another volcano or eruption (sometimes far from the one that is the subject of the manuscript) may produce a citation that is not at all apparent from the title.
Byers F M, 1959. Geology of Umnak and Bogoslof Islands, Aleutian Islands, Alaska. U S Geol Surv Bull, 1028-L: 267-365.
Coats R R, 1950. Volcanic activity in the Aleutian Arc. U S Geol Surv Bull, 974-B: 35-47.
IAVCEI, 1973-80. Post-Miocene Volcanoes of the World. IAVCEI Data Sheets, Rome: Internatl Assoc Volc Chemistry Earth's Interior..
Miller T P, McGimsey R G, Richter D H, Riehle J R, Nye C J, Yount M E, Dumoulin J A, 1998. Catalogue of the historically active volcanoes of Alaska. U S Geol Surv Open-File Rpt, 98-582: 1-104.
Motyka R J, Liss S A, Nye C J, Moorman M A, 1993. Geothermal resources of the Aleutian arc. Alaska Div Geol Geophys Surv, Prof Rpt, no 114, 17 p and 4 map sheets.
Smith R L, Shaw H R, Luedke R G, Russell S L, 1978. Comprehensive tables giving physical data and thermal energy estimates for young igneous systems of the United States. U S Geol Surv Open-File Rpt, 78-925: 1-25.