Ahyi

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  • Country
  • Volcanic Region
  • Primary Volcano Type
  • Last Known Eruption
  • 20.42°N
  • 145.03°E

  • -75 m
    -246 ft

  • 284141
  • Latitude
  • Longitude

  • Summit
    Elevation

  • Volcano
    Number

21 May-27 May 2014

On 23 May the USGS reported that during the previous week one explosion signal from the source at or near Ahyi seamount was detected. Seismic activity had been low since 8 May continuing to indicate that the eruption had possibly paused or ended.

Source: Emergency Management Office of the Commonwealth of the Mariana Islands and United States Geological Survey Volcano Hazards Program

Index of Weekly Reports


2014: April | May

Weekly Reports


21 May-27 May 2014

On 23 May the USGS reported that during the previous week one explosion signal from the source at or near Ahyi seamount was detected. Seismic activity had been low since 8 May continuing to indicate that the eruption had possibly paused or ended.

Source: Emergency Management Office of the Commonwealth of the Mariana Islands and United States Geological Survey Volcano Hazards Program


14 May-20 May 2014

On 16 May the USGS reported that during the previous week seismic signals from the source at or near Ahyi seamount had greatly diminished, indicating that the eruption had possibly paused or ended. Scientists aboard the research ship Hi'ialakai conducted water column tests in the vicinity of Ahyi on 15 May and reported no sign of activity, suggesting that the eruption occurred from a nearby volcanic vent and not the summit. The Aviation Color Code remained at Yellow and the Volcano Alert Level remained at Advisory.

Source: Emergency Management Office of the Commonwealth of the Mariana Islands and United States Geological Survey Volcano Hazards Program


7 May-13 May 2014

A helicorder plot from a station on Pagan showed that seismic signals from a source at or near the Ahyi seamount stopped at 1610 on 8 May. An additional isolated event was reported at 1810.

Source: Matthew Haney, Alaska Volcano Observatory via Bill Chadwick, Oregon State University's Marine Science Center and NOAA/PMEL EOI Program, personal communication


30 April-6 May 2014

Seismic stations on Pagan, Sarigan, Anatahan, and Saipan started recording signals on 24 April that continued at least through 2 May. The source had not been confirmed, but is thought to be at or near the Ahyi seamount. During 4-5 May a helicorder plot from a station on Pagan showed explosive signals at a rate of 20 per hour.

Sources: Emergency Management Office of the Commonwealth of the Mariana Islands and United States Geological Survey Volcano Hazards Program; Matthew Haney, Alaska Volcano Observatory via Bill Chadwick, Oregon State University's Marine Science Center and NOAA/PMEL EOI Program, personal communication


23 April-29 April 2014

Seismic stations on Pagan, Sarigan, Anatahan, and Saipan began recording signals starting at 0635 on 24 April believed to be from an undersea volcanic source. Hydroacoustic sensors on Wake Island suggested that the source is at or near Ahyi seamount, although it was possible that the vent is located at one of the other volcanic seamounts in the area. While conducting coral reef research at Farallon de Pajaros, NOAA divers reported hearing loud explosions and feeling the shock waves. One of the more powerful explosions was felt by the crew as it reverberated through the hull of the ship. On 27 April the Color Code was raised from Unassigned to Yellow. A report issued at 0536 on 30 April noted that seismic activity remained high.

Sources: Emergency Management Office of the Commonwealth of the Mariana Islands and United States Geological Survey Volcano Hazards Program; Bill Chadwick, Oregon State University's Marine Science Center and NOAA/PMEL EOI Program, personal communication


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.

11/1979 (SEAN 04:11) Shocks and sulfur upwelling

05/2001 (BGVN 26:05) Brief explosive activity on 24 April 2001 detected seismically

02/2014 (BGVN 39:02) Hydroacoustics and bathymetry aid in finding source of April-May 2014 submarine eruption


Contents of Monthly Reports

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

All times are local (= UTC + 10 hours)

11/1979 (SEAN 04:11) Shocks and sulfur upwelling

The crew of the fishing boat Koyo-maru 5 felt a series of shocks beginning at about 1530 on 15 November, followed by the upwelling of water containing sulfur about 15 km SE of Farallon de Pajaros Island at 20.445°N, 145.03°E. Depths in the area of the activity range from 70 to 200 m. The JMSA reports that sea surface discoloration has been observed there in the past.

Since the day before, a larger than normal cloud plume had been observed over Farallon de Pajaros.

Information Contacts: JMSA, Tokyo; JMA, Tokyo; T. Tiba, National Science Museum, Tokyo.

05/2001 (BGVN 26:05) Brief explosive activity on 24 April 2001 detected seismically

A short episode of explosive submarine volcanism was recorded 24 April 2001 by the Laboratoire de Géophysique's (LDG) Pomariorio (PMO) seismic station on Rangiroa Atoll, Tuamotu Archipelago. This episode began at 1110 UTC, and ended at 1900 UTC, with more than 40 explosive T-waves at a fairly uniform rate. The wave forms were similar to those of December 1989 (from a source NW of Supply Reef, SEAN 14:12), and suggested a source in the Mariana Islands. LDG scientists identified these explosive events on records from some other IRIS and Freesia stations, and computed a well-constrained location at 20.34°N, 145.02°E with an error of 15 km (figure 1).

Figure 1. Map showing Ahyi and other volcanic edifices along part of the Mariana Arc just north of 20°N, 145°E. The location of the April 2001 activity is indicated, as well as activity reported between Farallon de Pajaros and Supply Reef in 1967, 1969, 1979, 1985, and 1989. Contour interval is 200 m; bathymetry is based on US Navy narrow-beam SASS data. Thick black bars show 1985 dredge locations. Scale and volcanic activity locations are approximate. Base map modified from Bloomer and others (1989).

The summit of Ahyi lies within this location uncertainty, approximately 10 km N. Ahyi seamount is a large conical submarine volcano that rises to within about 140 m of the sea surface about 18 km SE of Farallon de Pajaros. Water discoloration has been observed over the volcano, and in 1979 the crew of a fishing boat felt shocks over the summit area followed by upwelling of sulfur-bearing water (SEAN 04:11).

Regional volcanic activity. Most of the recent historical activity in this area is based on acoustic detection methods from great distances, making exact location determinations difficult. The following presents background information about other volcanoes close to the April 2001 event, with a description of recent volcanism.

The small 2-km-wide island of Farallon de Pajaros (also known as Uracas) is the northernmost and most active volcano of the Mariana Islands. Its relatively frequent historical eruptions dating back to the mid-19th century have caused it to be referred to as the "lighthouse of the western Pacific." Flank fissures have fed historical lava flows that form platforms along the coast. Summit vents have also been active during historical time, and eruptions have been observed from nearby submarine vents. Aerial observations of fuming were reported in July 1981 (with discolored water), August 1990, and May 1992. Makhahnas seamount, which rises to within 640 m of the sea surface, lies about 10 km SW. A possible eruption during March-April 1967 on the SW flank of this seamount was identified on the basis of T-phase recordings by Norris and Johnson (1969).

Supply Reef is a conical submarine volcano that rises to within 8 m of the sea surface. The seamount lies about 10 km NW of the Maug Islands, the emergent summit of a submarine volcano that is joined to Supply Reef by a low saddle at a depth of about 1,800 m. Several submarine eruptions have been detected by sonar signals originating from points very approximately located at distances of 15-25 km NW of Supply Reef. An event in March 1969 was detected using T-phase recordings and located by the crew of a fishing boat who heard explosion sounds and saw water discoloration (CSLP Cards 528 and 534). Activity in August-September 1985 (SEAN 10:09 and 10:11) and September and December 1989 (SEAN 14:10 and 14:12) were in the same approximate location, 30 km S of Farallon de Pajaros, about midway between Makhahnas and Supply Reef. Both of these events were identified and located using T-phase data, but discolored water was also observed during the 1985 event by an airline pilot.

References. Bloomer, S.H., Stern, R.J., and Smoot, N.C., 1989, Physical volcanology of the submarine Mariana and Volcano arcs: Bulletin of Volcanology, v. 51, p. 210-224.

Norris, R.A., and Johnson, R.H., 1969, Submarine volcanic eruptions recently located in the Pacific by Sofar hydrophones: Journal of Geophysical Research, v. 74, no. 2, p. 650-664.

Information Contact: Olivier Hyvernaud, Laboratoire de Géophysique, PO Box 640, Pamatai, Tahiti, French Polynesia (Email: hyvernaud@labogeo.pf or LDG@mail.pf).

02/2014 (BGVN 39:02) Hydroacoustics and bathymetry aid in finding source of April-May 2014 submarine eruption

An HTML version of this report is not available, please read this report as a PDF file. Note that this report was revised as of August 2014.

Ahyi seamount is a large conical submarine volcano that rises to an estimated 75 m of the sea surface about 18 km SE of the island of Farallon de Pajaros (Uracas) in the northern Marianas. Water discoloration has been observed over the seamount, and in 1979 the crew of a fishing boat felt shocks over the summit area followed by upwelling of sulfur-bearing water. On 24-25 April 2001 an explosive eruption was detected seismically by a station on Rangiroa Atoll, Tuamotu Archipelago. The event was well constrained (+/- 15 km) at a location near the southern base of Ahyi; the summit of the seamount lies within the location uncertainty. An eruption in 2014 was detected by NOAA divers, hydroacoustic sensors, and seismic stations.

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

Start Date Stop Date Eruption Certainty VEI Evidence Activity Area or Unit
2014 Apr 24 2014 May 8 (?) Confirmed 0 Hydrophonic
2001 Apr 24 2001 Apr 25 Confirmed 0 Hydrophonic 20.34°N, 145.02°E
[ 1979 Nov 15 ] [ Unknown ] Uncertain 0  

The Global Volcanism Program has no synonyms or subfeatures listed for Ahyi.

The Omanago volcano group (upper left) consists of a series of five closely spaced lava domes in Nikko National Park. The highest of the dacitic domes is 2367-m-high Omanago, located at the SE end of the complex. Mitsu-dake, the NW-most dome, is a complex lava dome. The higher northern peak of the Mitsu-dake complex is out of view to the left, and the lower southern dome forms the low ridge behind the hot spring resort of Yunoko lake in the center of the photo. The prominent peak on the right horizon is Nantai volcano.

Photo by Lee Siebert, 1964 (Smithsonian Institution).
Ahyi seamount (upper right) is a large conical submarine volcano that rises to within 137 m of the sea surface about 18 km SE of the island of Farallon de Pajaros (left-center). At various times since 1979, water discoloration, felt shocks followed by upwelling of sulfur-bearing water, and a seismically detected submarine eruption have been reported at or near Ahyi seamount. Two submarine volcanoes on the flanks of Farallon de Pajaros, Northwest Uracas and Makhahnas, are seen in this NOAA bathymetric image.

Image courtesy of NOAA, 2003 (http://oceanexplorer.noaa.gov/explorations/03fire/logs/mar02/media/nikko.html).
Ahyi submarine volcano is seen in a bathymetric view looking from the NE with two times vertical exaggeration. Ahyi seamount is a large conical submarine volcano that rises to within 137 m of the sea surface about 18 km SE of the island of Farallon de Pajaros (Uracas) in the northern Marianas. Water discoloration has been observed over the submarine volcano, and an explosive eruption was seismically detected in April 2001.

Image courtesy of Susan Merle (Oregon State University/NOAA Vents Program).

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.

Bloomer S H, Stern R J, Fisk E, Geschwind C H, 1989. Shoshonitic volcanism in the northern Mariana Arc 1. Mineralogic and major and trace element characteristics. J Geophys Res, 94: 4469-4496.

Bloomer S H, Stern R J, Smoot N C, 1989. Physical volcanology of the submarine Mariana and Volcano arcs. Bull Volc, 51: 210-224.

Smithsonian Institution-GVN, 1990-. [Monthly event reports]. Bull Global Volc Network, v 15-33.

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

Volcano Types

Submarine

Tectonic Setting

Subduction zone
Crustal thickness unknown

Rock Types

Major
Andesite / Basaltic Andesite
Basalt / Picro-Basalt

Population

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

Affiliated Databases

Large Eruptions of Ahyi 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.