Seguam

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  • United States
  • Alaska
  • Stratovolcano(es)
  • 1993 CE
  • Country
  • Volcanic Region
  • Primary Volcano Type
  • Last Known Eruption
  • 52.315°N
  • 172.51°W

  • 1054 m
    3457 ft

  • 311180
  • Latitude
  • Longitude

  • Summit
    Elevation

  • Volcano
    Number

The Global Volcanism Program has no activity reports for Seguam.

The Global Volcanism Program has no Weekly Reports available for Seguam.

Index of Monthly Reports

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.

03/1977 (SEAN 02:03) Lava fountaining from a 1-km-long rift seen on 6 March

12/1992 (BGVN 17:12) Small ash eruptions

05/1993 (BGVN 18:05) Ash eruptions reported

07/1993 (BGVN 18:07) Ash eruptions to 2,400 m height; lava flow

08/1993 (BGVN 18:08) Ash eruption to 2,500 m altitude


Contents of Monthly Reports

All information contained in these reports is preliminary and subject to change.

All times are local (= UTC - 9 hours)

03/1977 (SEAN 02:03) Lava fountaining from a 1-km-long rift seen on 6 March

Jürgen Kienle reported that on 6 March at about 0400, the crew of the USCG Cutter Mellon observed and photographed eruptive activity at the 750-m level of Pyre Peak, Seguam Island. Eight lava fountains rising to an estimated 90 m were observed along a l-km radial rift 2.5 km SW of Pyre Peak summit. Activity appeared to be progressing NE (towards the summit).

A lava flow formed and divided into two tongues. The larger was approximately 2.5 km long and l km wide. The smaller moved toward the S, and was approximately l km long and 0.5 km wide. Three dense black clouds were erupted from the vent during 2 hours of observation, after which the Mellon departed.

The nearest short-period seismometers, 225 km to the E (Nikolski), and 300 km to the W (Adak), were too far away to register any unusual earthquake activity.

Thomas Miller reported that on 8 March, a Reeve Aleutian Airlines flight passed over Seguam at low altitude. The pilot reported that lava effusion and fountaining had ended, but that a considerable amount of steam, possibly containing some ash, was being emitted from the fissure. Lava flows had not reached the sea. Poor weather during much of the year hampers aerial observation.

Several other ship reports of eruptions in the area have been received in the past several years. Seguam is uninhabited.

Information Contacts: J. Kienle, Univ. of Alaska; T. Miller, USGS, Anchorage.

12/1992 (BGVN 17:12) Small ash eruptions

Small ash eruptions from a satellite cone 1.5 km S of the W caldera's central cone (Pyre Peak) (figure 1) were observed on 27 and 30 December 1992 by the U.S. Coast Guard . . . . Activity on the 27th consisted of an ash plume that extended 24 km N from the island at 1,200 m altitude. On 30 December, discrete explosions ejected ash to several hundred meters height. Ash fell S of the vent, which appears to be located near the N end of a line of lava fountains observed during the 1977 eruption. The vent site consists of a cluster of cinder cones and craters, which was probably the source of a prehistoric basaltic lava field covering ~21 km2.

Figure 1. Topographic map of Seguam Island showing the area of December 1992 activity (dot S of Pyre Peak). The line SE from the vent site represents the 1977 lava fountains, and the outline shows the 1977 lava flows. Courtesy of AVO.

Information Contacts: Michael Doukas, USGS Anchorage.

05/1993 (BGVN 18:05) Ash eruptions reported

A small ash burst, rising through clouds near Pyre Peak, was reported by the U.S. Coast Guard on 28 May. A plume to 3 km altitude was reported on 2 June by the NWS, but it is not known if the plume contained ash.

Information Contacts: AVO.

07/1993 (BGVN 18:07) Ash eruptions to 2,400 m height; lava flow

Heavy ash eruptions rising 900-1,200 m were reported the morning of 31 July by the U.S. Coast Guard. A lava flow was also noted. According to these observers, the volcano was still erupting sporadically on 10 August, with light- to dark-gray ash plumes rising 2,400 m above the summit. Reports from Atka Island (~110 km W) indicate that weather conditions have frequently prevented observations.

Information Contacts: AVO.

08/1993 (BGVN 18:08) Ash eruption to 2,500 m altitude

On 19 August, U.S. Coast Guard observers reported that Pyre Peak . . . was continuing to erupt from a vent ~180 m below the summit. A dark ash plume over the volcano that day reached an altitude of 2,500 m and drifted ESE. No reports of ashfall in the sparsely populated region were received. U.S. Coast Guard observers reported that Pyre Peak was continuing to erupt in late August, but poor weather conditions prevented observers from confirming continued activity through 3 September. Frequent poor weather and limited air traffic combine to make tracking of activity at this remote island volcano difficult.

Information Contacts: AVO.

The elliptical, 11.5 x 24 km island of Seguam, lying between Amlia and Amukta Islands in the central Aleutians, contains two calderas with Holocene post-caldera cones. Growth of the basaltic-to-rhyolitic Wilcox volcano on the east side of the island during the late Pleistocene was followed by edifice collapse and an associated ignimbrite eruption about 9000 years ago, leaving a horseshoe-shaped caldera open to the west, inside which a rhyolitic cone was constructed. The 3 x 4 km wide westernmost caldera has a central scoria cone, Pyre Peak, which rises above the caldera rim and is the source of most of the historical eruptions of Seguam volcano. A very young basaltic field surrounds Pyre Peak, and lava flows partially fill the caldera and reach the southern coast. Older Holocene lava flows were erupted from vents within the eastern caldera, and a monogenetic Holocene cone forms Moundhill volcano on the eastern tip of the island.

Summary of Holocene eruption dates and Volcanic Explosivity Indices (VEI).

Start Date Stop Date Eruption Certainty VEI Evidence Activity Area or Unit
1993 May 28 1993 Aug 31 (in or after) Confirmed 2 Historical Observations Near Pyre Peak
1992 Dec 27 1992 Dec 30 Confirmed 2 Historical Observations Pyre Peak (1.5 km south of summit)
1977 Mar 6 1977 Mar 8 (?) Confirmed 1 Historical Observations Pyre Peak (2.5 km SE of summit)
[ 1927 ] [ Unknown ] Uncertain    
1902 Unknown Confirmed 3 Historical Observations
1892 Apr 15 ± 45 days Unknown Confirmed 3 Historical Observations
1891 Dec Unknown Confirmed 2 Historical Observations
[ 1827 ] [ Unknown ] Uncertain    
1786 1790 Confirmed   Historical Observations
0250 ± 500 years Unknown Confirmed   Uranium-series West of Wilcox volcano
4050 BCE ± 4000 years Unknown Confirmed 0 Uranium-series W flank of cone in eastern caldera
5100 BCE ± 2000 years Unknown Confirmed 0 Uranium-series W flank of cone in eastern caldera
7300 BCE ± 2250 years Unknown Confirmed 5 Ar/Ar Wilcox volcano

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.



Synonyms
Siguam | Goreli | Giguan


Cones
Feature Name Feature Type Elevation Latitude Longitude
Moundhill Lava cone 587 m 52° 21' 0" N 172° 19' 0" W
Pyre Peak Cinder cone 1054 m 52° 19' 0" N 172° 31' 0" W
Wilcox Stratovolcano 52° 19' 30" N 172° 21' 0" W
Lava fountains rise above a fissure on Seguam volcano on March 8, 1977. This view from the south shows part of the 1.5-km-long eruptive fissure SE of Pyre Peak, the volcano's summit. Black lava flows move across the snow from the fissure and diverge around an older, snow-covered cone at the lower right. Two large late-Quaternary calderas occur on Seguam Island, both of which contain Holocene cones. Pyre Peak, in the western caldera, is surrounded by fresh lava fields and dominates the western half of the island.

Photo by U.S. Coast Guard, 1977 (courtesy of Alaska Volcano Observatory).
The snow-dappled slopes of Pyre Peak are seen from near the western tip of Seguam Island. The elliptical, 11.5 x 24 km island contains two calderas, each with a Holocene central volcano. A third Holocene cone lies at the eastern end of the island. Pyre Peak was constructed within the 3-km-wide westernmost caldera. The 1054-m-high cone rises 1 km above the caldera floor and has been the source of most of the historical eruptions of Seguam volcano.

Photo by Steve Ebbert, 1996 (U.S. Fish and Wildlife Service).

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.

Coats R R, 1950. Volcanic activity in the Aleutian Arc. U S Geol Surv Bull, 974-B: 35-47.

Henning R A, Rosenthal C H, Olds B, Reading E (eds), 1976. Alaska's volcanoes, northern link in the ring of fire. Alaska Geog, 4: 1-88.

IAVCEI, 1973-80. Post-Miocene Volcanoes of the World. IAVCEI Data Sheets, Rome: Internatl Assoc Volc Chemistry Earth's Interior..

Jicha B R, Singer B S, 2006. Volcanic history and magmatic evolution of Seguam Island, Aleutian Island arc, Alaska. Geol Soc Amer Bull, 118: 805-822.

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.

Myers J D, 1994. The Geology, Geochemistry and Petrology of the recent Magmatic Phase of the Central and Western Aleutian Arc. Unpublished manuscript, unpaginated.

Singer B S, Myers J D, Frost C D, 1992. Mid-Pleistocene lavas from the Seguam volcanic center, central Aleutian arc: closed-system fractional crystallization of a basalt to rhyodacite eruptive suite. Contr Mineral Petr, 110: 87-112.

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.

Smithsonian Institution-SEAN, 1975-89. [Monthly event reports]. Bull Scientific Event Alert Network (SEAN), v 1-14.

Wood C A, Kienle J (eds), 1990. Volcanoes of North America. Cambridge, England: Cambridge Univ Press, 354 p.

Volcano Types

Stratovolcano(es)
Caldera(s)

Tectonic Setting

Subduction zone
Intermediate crust (15-25 km)

Rock Types

Major
Andesite / Basaltic Andesite
Dacite
Basalt / Picro-Basalt
Minor
Rhyolite

Population

Within 5 km
Within 10 km
Within 30 km
Within 100 km
0
0
0
0

Affiliated Databases

Large Eruptions of Seguam Information about large Quaternary eruptions (VEI >= 4) is cataloged in the Large Magnitude Explosive Volcanic Eruptions (LaMEVE) database of the Volcano Global Risk Identification and Analysis Project (VOGRIPA).
WOVOdat WOVOdat is a database of volcanic unrest; instrumentally and visually recorded changes in seismicity, ground deformation, gas emission, and other parameters from their normal baselines. It is sponsored by the World Organization of Volcano Observatories (WOVO) and presently hosted at the Earth Observatory of Singapore.
EarthChem EarthChem develops and maintains databases, software, and services that support the preservation, discovery, access and analysis of geochemical data, and facilitate their integration with the broad array of other available earth science parameters. EarthChem is operated by a joint team of disciplinary scientists, data scientists, data managers and information technology developers who are part of the NSF-funded data facility Integrated Earth Data Applications (IEDA). IEDA is a collaborative effort of EarthChem and the Marine Geoscience Data System (MGDS).
Smithsonian Collections Search the Smithsonian's NMNH Department of Mineral Sciences collections database. Go to the "Search Rocks and Ores" tab and use the Volcano Name drop-down to find samples.