New activity/unrest was observed at 3 volcanoes from May 21 – 27, 2014. Ongoing activity was reported for 11 volcanoes.
New activity/unrest: Ahyi, Mariana Islands (USA) | San Miguel, El Salvador | Santa María, Guatemala
Ongoing activity: Aira, Kyushu (Japan) | Bagana, Bougainville (Papua New Guinea) | Batu Tara, Komba Island (Indonesia) | Dukono, Halmahera (Indonesia) | Karymsky, Eastern Kamchatka (Russia) | Kilauea, Hawaiian Islands (USA) | Merapi, Central Java (Indonesia) | Reventador, Ecuador | Shishaldin, Fox Islands (USA) | Shiveluch, Central Kamchatka (Russia) | Ubinas, Peru
The Weekly Volcanic Activity Report is a cooperative project between the Smithsonian's Global Volcanism Program and the US Geological Survey's Volcano Hazards Program. Updated by 23:00 UTC every Wednesday, notices of volcanic activity posted on these pages are preliminary and subject to change as events are studied in more detail.
Ahyi, Mariana Islands (USA)
20.42°N, 145.03°E, Summit elev. -137 m
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.
Geologic summary: 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 in 1979 the crew of a fishing boat felt shocks over the summit area of the seamount followed by upwelling of sulfur-bearing water. On April 24-25, 2001 an explosive submarine eruption was detected seismically from a seismic 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.
San Miguel, El Salvador
13.434°N, 88.269°W, Summit elev. 2130 m
According to SNET, the Ministerio de Medio Ambiente y Recursos Naturales (MARN) reported that during 22-23 May heavy rains at San Miguel caused lahars that originated from the upper part of the volcano and were heard by residents. Seismicity and gas output both remained high. Gas plumes rose 300 m and drifted W; the plumes were different colors and suggested that fine material was being carried out of the crater.
Geologic summary: The symmetrical cone of San Miguel volcano, one of the most active in El Salvador, rises from near sea level to form one of the country's most prominent landmarks. The unvegetated summit of the 2130-m-high volcano rises above slopes draped with coffee plantations. A broad, deep crater complex that has been frequently modified by historical eruptions (recorded since the early 16th century) caps the truncated summit of the towering volcano, which is also known locally as Chaparrastique. Radial fissures on the flanks of the basaltic-andesitic volcano have fed a series of historical lava flows, including several erupted during the 17th-19th centuries that reached beyond the base of the volcano on the north, NE, and SE sides. The SE-flank lava flows are the largest and form broad, sparsely vegetated lava fields crossed by highways and a railroad skirting the base of the volcano. The location of flank vents has migrated higher on the edifice during historical time, and the most recent activity has consisted of minor ash eruptions from the summit crater.
Santa María, Guatemala
14.756°N, 91.552°W, Summit elev. 3772 m
INSIVUMEH reported that on 22 May a lahar, the second since the 9 May eruption at Santa María's Santiaguito lava-dome complex, carried blocks up to 1 m in diameter as well as tree trunks. The lahar was 15 m wide and 2 m deep and had a strong sulfur odor. An explosion at 0608 on 23 May generated an ash plume that rose 700 m, drifted SW, and caused ashfall in parts of Monte Claro (S). On 24 May a lahar that was 25 m wide, 2 m deep, and had a sulfur odor descended the Nima I drainage, carrying tree trunks and branches. During 26-27 May gas-and-ash plumes rose 300-500 m and drifted SW.
Geologic summary: Symmetrical, forest-covered Santa María volcano is one of the most prominent of a chain of large stratovolcanoes that rises dramatically above the Pacific coastal plain of Guatemala. The 3772-m-high stratovolcano has a sharp-topped, conical profile that is cut on the SW flank by a large, 1.5-km-wide crater. The oval-shaped crater extends from just below the summit of Volcán Santa María to the lower flank and was formed during a catastrophic eruption in 1902. The renowned plinian eruption of 1902 that devastated much of SW Guatemala followed a long repose period after construction of the large basaltic-andesite stratovolcano. The massive dacitic Santiaguito lava-dome complex has been growing at the base of the 1902 crater since 1922. Compound dome growth at Santiaguito has occurred episodically from four westward-younging vents, the most recent of which is Caliente. Dome growth has been accompanied by almost continuous minor explosions, with periodic lava extrusion, larger explosions, pyroclastic flows, and lahars.
Aira, Kyushu (Japan)
31.593°N, 130.657°E, Summit elev. 1117 m
JMA reported that during 19-23 May two explosions from Showa Crater at Aira Caldera’s Sakurajima volcano ejected tephra as far as 1,300 m. Incandescence from the crater was detected at night during 19-20 May. The Alert Level remained at 3 (on a scale of 1-5). The Tokyo VAAC reported that during 23-25 May plumes rose to altitudes of 2.4-4 km (8,000-13,000 ft) a.s.l. and drifted S, SE, and N.
Geologic summary: The Aira caldera in the northern half of Kagoshima Bay contains the post-caldera Sakurajima volcano, one of Japan's most active. Eruption of the voluminous Ito pyroclastic flow accompanied formation of the 17 x 23 km caldera about 22,000 years ago. The smaller Wakamiko caldera was formed during the early Holocene in the NE corner of the Aira caldera, along with several post-caldera cones. The construction of Sakurajima began about 13,000 years ago on the southern rim of Aira caldera and built an island that was finally joined to the Osumi Peninsula during the major explosive and effusive eruption of 1914. Activity at the Kitadake summit cone ended about 4850 years ago, after which eruptions took place at Minamidake. Frequent historical eruptions, recorded since the 8th century, have deposited ash on Kagoshima, one of Kyushu's largest cities, located across Kagoshima Bay only 8 km from the summit. The largest historical eruption took place during 1471-76.
Bagana, Bougainville (Papua New Guinea)
6.14°S, 155.195°E, Summit elev. 1750 m
Based on analyses of satellite imagery and wind data, the Darwin VAAC reported that on 27 May an ash plume from Bagana rose to an altitude of 3 km (10,000 ft) a.s.l. and drifted 65 km W.
Geologic summary: Bagana volcano, occupying a remote portion of central Bougainville Island, is one of Melanesia's youngest and most active volcanoes. Bagana is a massive symmetrical, roughly 1750-m-high lava cone largely constructed by an accumulation of viscous andesitic lava flows. The entire lava cone could have been constructed in about 300 years at its present rate of lava production. Eruptive activity at Bagana is frequent and is characterized by non-explosive effusion of viscous lava that maintains a small lava dome in the summit crater, although explosive activity occasionally producing pyroclastic flows also occurs. Lava flows form dramatic, freshly preserved tongue-shaped lobes up to 50-m-thick with prominent levees that descend the volcano's flanks on all sides.
Batu Tara, Komba Island (Indonesia)
7.792°S, 123.579°E, Summit elev. 748 m
Based on analyses of satellite imagery and wind data, the Darwin VAAC reported that during 26-27 May ash plumes from Batu Tara rose to altitudes of 1.2-2.1 km (4,000-7,000 ft) a.s.l. and drifted 25-95 km NW and W.
Geologic summary: The small isolated island of Batu Tara in the Flores Sea about 50 km north of Lembata (fomerly Lomblen) Island contains a scarp on the eastern side similar to the Sciara del Fuoco of Italy's Stromboli volcano. Vegetation covers the flanks of Batu Tara to within 50 m of the 748-m-high summit. Batu Tara lies north of the main volcanic arc and is noted for its potassic leucite-bearing basanitic and tephritic rocks. The first historical eruption from Batu Tara, during 1847-52, produced explosions and a lava flow.
Dukono, Halmahera (Indonesia)
1.68°N, 127.88°E, Summit elev. 1335 m
Based on analyses of satellite imagery and wind data, the Darwin VAAC reported that on 24 May ash plumes from Dukono rose to an altitude of 3.4 km (11,000 ft) a.s.l. and drifted 65 km W.
Geologic summary: Reports from this remote volcano in northernmost Halmahera are rare, but Dukono has been one of Indonesia's most active volcanoes. More-or-less continuous explosive eruptions, sometimes accompanied by lava flows, occurred from 1933 until at least the mid-1990s, when routine observations were curtailed. During a major eruption in 1550, a lava flow filled in the strait between Halmahera and the north-flank cone of Gunung Mamuya. Dukono is a complex volcano presenting a broad, low profile with multiple summit peaks and overlapping craters. Malupang Wariang, 1 km SW of Dukono's summit crater complex, contains a 700 x 570 m crater that has also been active during historical time.
Karymsky, Eastern Kamchatka (Russia)
54.05°N, 159.45°E, Summit elev. 1536 m
KVERT reported that Strombolian and weak Vulcanian activity continued at Karymsky during 16-23 May. The Aviation Color Code remained at Orange.
Geologic summary: Karymsky, the most active volcano of Kamchatka's eastern volcanic zone, is a symmetrical stratovolcano constructed within a 5-km-wide caldera that formed during the early Holocene. The caldera cuts the south side of the Pleistocene Dvor volcano and is located outside the north margin of the large mid-Pleistocene Polovinka caldera, which contains the smaller Akademia Nauk and Odnoboky calderas. Most seismicity preceding Karymsky eruptions originated beneath Akademia Nauk caldera, which is located immediately south of Karymsky volcano. The caldera enclosing Karymsky volcano formed about 7600-7700 radiocarbon years ago; construction of the Karymsky stratovolcano began about 2000 years later. The latest eruptive period began about 500 years ago, following a 2300-year quiescence. Much of the cone is mantled by lava flows less than 200 years old. Historical eruptions have been vulcanian or vulcanian-strombolian with moderate explosive activity and occasional lava flows from the summit crater.
Kilauea, Hawaiian Islands (USA)
19.421°N, 155.287°W | Summit elev. 1222 m
During 21-27 May HVO reported that the circulating lava lake occasionally rose and fell in the deep pit within Kilauea's Halema'uma'u Crater. Gas emissions remained elevated. The plume from the vent continued to deposit variable amounts of ash, spatter, and Pele's hair onto nearby areas; smaller particles may have been dropped several kilometers away.
At Pu'u 'O'o Crater, glow emanated from spatter cones on the N, NE, SE, and S portions of the crater floor. The Kahauale’a 2 lava flow continued to advance, with breakouts from the main stalled lobe, and burn adjoining forest. On 22 May geologists mapped the farthest point of activity, 8.4 km NE of Pu’u 'O'o.
Geologic summary: Kilauea volcano, which overlaps the east flank of the massive Mauna Loa shield volcano, has been Hawaii's most active volcano during historical time. Eruptions of Kilauea are prominent in Polynesian legends; written documentation extending back to only 1820 records frequent summit and flank lava flow eruptions that were interspersed with periods of long-term lava lake activity that lasted until 1924 at Halemaumau crater, within the summit caldera. The 3 x 5 km caldera was formed in several stages about 1500 years ago and during the 18th century; eruptions have also originated from the lengthy East and SW rift zones, which extend to the sea on both sides of the volcano. About 90% of the surface of the basaltic shield volcano is formed of lava flows less than about 1100 years old; 70% of the volcano's surface is younger than 600 years. A long-term eruption from the East rift zone that began in 1983 has produced lava flows covering more than 100 sq km, destroying nearly 200 houses and adding new coastline to the island.
Merapi, Central Java (Indonesia)
7.542°S, 110.442°E, Summit elev. 2968 m
PVMBG reported that seismicity at Merapi decreased during 16-22 May, as compared to the previous week. No deformation was detected. The Alert Level was lowered to 1 (on a scale of 1-4) on 23 May.
Geologic summary: Merapi, one of Indonesia's most active volcanoes, lies in one of the world's most densely populated areas and dominates the landscape immediately north of the major city of Yogyakarta. Merapi is the youngest and southernmost of a volcanic chain extending NNW to Ungaran volcano. Growth of Old Merapi volcano beginning during the Pleistocene ended with major edifice collapse perhaps about 2000 years ago, leaving a large arcuate scarp cutting the eroded older Batulawang volcano. Subsequently growth of the steep-sided Young Merapi edifice, its upper part unvegetated due to frequent eruptive activity, began SW of the earlier collapse scarp. Pyroclastic flows and lahars accompanying growth and collapse of the steep-sided active summit lava dome have devastated cultivated lands on the volcano's western-to-southern flanks and caused many fatalities during historical time. The volcano is the object of extensive monitoring efforts by the Merapi Volcano Observatory.
0.077°S, 77.656°W, Summit elev. 3562 m
IG reported that although cloud cover often prevented observations of Reventador during 21-27 May ash plumes were occasionally observed. An ash plume was observed from an aircraft on 22 May, and the next day an ash-and-vapor plume rose 1 km and drifted NW.
Geologic summary: Reventador is the most frequently active of a chain of Ecuadorian volcanoes in the Cordillera Real, well east of the principal volcanic axis. The forested, dominantly andesitic Volcán El Reventador stratovolcano rises to 3562 m above the jungles of the western Amazon basin. A 4-km-wide caldera widely breached to the east was formed by edifice collapse and is partially filled by a young, unvegetated stratovolcano that rises about 1300 m above the caldera floor to a height comparable to the caldera rim. Reventador has been the source of numerous lava flows as well as explosive eruptions that were visible from Quito in historical time. Frequent lahars in this region of heavy rainfall have constructed a debris plain on the eastern floor of the caldera. The largest historical eruption at Reventador took place in 2002, producing a 17-km-high eruption column, pyroclastic flows that traveled up to 8 km, and lava flows from summit and flank vents.
Shishaldin, Fox Islands (USA)
54.756°N, 163.97°W, Summit elev. 2857 m
AVO reported that on most days during 21-27 May elevated surface temperatures at Shishaldin's summit were detected in satellite images, and minor steam emissions were observed in webcam images on 21 May. Cloud cover often prevented observations. Seismometers near the volcano detected brief explosion signals during 21-26 May. The Aviation Color Code remained at Orange and the Volcano Alert Level remained at Watch.
Geologic summary: The beautifully symmetrical volcano of Shishaldin is the highest and one of the most active volcanoes of the Aleutian Islands. The 2857-m-high, glacier-covered volcano is the westernmost of three large stratovolcanoes along an E-W line in the eastern half of Unimak Island. The Aleuts named the volcano Sisquk, meaning "mountain which points the way when I am lost." A steady steam plume rises from its small summit crater. Constructed atop an older glacially dissected volcano, Shishaldin is Holocene in age and largely basaltic in composition. Remnants of an older ancestral volcano are exposed on the west and NE sides at 1500-1800 m elevation. Shishaldin contains over two dozen pyroclastic cones on its NW flank, which is blanketed by massive aa lava flows. Frequent explosive activity, primarily consisting of strombolian ash eruptions from the small summit crater, but sometimes producing lava flows, has been recorded since the 18th century.
Shiveluch, Central Kamchatka (Russia)
56.653°N, 161.36°E, Summit elev. 3283 m
KVERT reported that during 16-23 May lava-dome extrusion onto Shiveluch’s SE flank was accompanied by ash explosions, incandescence, hot avalanches, and fumarolic activity. Satellite images detected a thermal anomaly over the dome on 16 and 19 May. Satellite images on 27 May showed ash plumes rising to altitudes of 3-10 km (9,800-32,800 ft) and drifted as far as 850 km S. The Aviation Color Code remained at Orange.
Geologic summary: The high, isolated massif of Shiveluch volcano (also spelled Sheveluch) rises above the lowlands NNE of the Kliuchevskaya volcano group. The 1300 cu km Shiveluch is one of Kamchatka's largest and most active volcanic structures. The summit of roughly 65,000-year-old Stary Shiveluch is truncated by a broad 9-km-wide late-Pleistocene caldera breached to the south. Many lava domes dot its outer flanks. The Molodoy Shiveluch lava dome complex was constructed during the Holocene within the large horseshoe-shaped caldera; Holocene lava dome extrusion also took place on the flanks of Stary Shiveluch. At least 60 large eruptions of Shiveluch have occurred during the Holocene, making it the most vigorous andesitic volcano of the Kuril-Kamchatka arc. Widespread tephra layers from these eruptions have provided valuable time markers for dating volcanic events in Kamchatka. Frequent collapses of dome complexes, most recently in 1964, have produced debris avalanches whose deposits cover much of the floor of the breached caldera.
16.355°S, 70.903°W, Summit elev. 5672 m
Observatorio Vulcanológico del INGEMMET (OVI) reported that during 21-23 and 25-27 May ash emissions at Ubinas continued. On most days gas-and-ash plumes rose 0.7-3.8 km above the crater and drifted W, N, E, and SE. Ashfall was reported in various towns downwind of the plumes including Querapi (4 km S), Ubinas (6.5 km SSE), Escacha, Lloque, Chojata, San Miguel, and Tonohaya.
Geologic summary: A small, 1.4-km-wide caldera cuts the top of Ubinas, Peru's most active volcano, giving it a truncated appearance. Ubinas is the northernmost of three young volcanoes located along a regional structural lineament about 50 km behind the main volcanic front of Perú. The growth and destruction of Ubinas I volcano was followed by construction of Ubinas II volcano beginning in the mid-Pleistocene. The upper slopes of the andesitic-to-rhyolitic Ubinas II stratovolcano are composed primarily of andesitic and trachyandesitic lava flows and steepen to nearly 45 degrees. The steep-walled, 150-m-deep summit caldera contains an ash cone with a 500-m-wide funnel-shaped vent that is 200 m deep. Debris-avalanche deposits from the collapse of the SE flank of Ubinas about 3700 years ago extend 10 km from the volcano. Widespread plinian pumice-fall deposits from Ubinas include one of Holocene age about 1000 years ago. Holocene lava flows are visible on the volcano's flanks, but historical activity, documented since the 16th century, has consisted of intermittent minor-to-moderate explosive eruptions.
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