Active volcanoes in the world: February 25 – March 3, 2015

New activity was observed at 6 volcanoes from February 25 – March 3, 2015. During the same period, ongoing activity was observed at 13 volcanoes.

New activity/unrest: Ambrym, Vanuatu | Chikurachki, Paramushir Island (Russia) | Fuego, Guatemala | Popocatepetl, Mexico | Sangay, Ecuador | Villarrica, Chile.

Ongoing activity: Aira, Kyushu (Japan) | Bardarbunga, Iceland | Chirpoi, Kuril Islands (Russia) | Colima, Mexico | Karymsky, Eastern Kamchatka (Russia) | Kilauea, Hawaiian Islands (USA) | Klyuchevskoy, Central Kamchatka (Russia) | Nishinoshima, Japan | Reventador, Ecuador | Sheveluch, Central Kamchatka (Russia) | Shishaldin, Fox Islands (USA) | Zhupanovsky, Eastern Kamchatka (Russia).

Ambrym, Vanuatu
16.25°S, 168.12°E, Elevation 1334 m

On 2 March the Vanuatu Geohazards Observatory reported that activity at Ambrym had slightly decreased but remained elevated. The Alert Level was lowered to 2 (on a new scale of 0-5). Areas deemed hazardous were near and around the active vents (Benbow, Maben-Mbwelesu, Niri-Mbwelesu and Mbwelesu), and in downwind areas prone to ashfall.

Geologic summary: Ambrym, a large basaltic volcano with a 12-km-wide caldera, is one of the most active volcanoes of the New Hebrides arc. A thick, almost exclusively pyroclastic sequence, initially dacitic, then basaltic, overlies lava flows of a pre-caldera shield volcano. The caldera was formed during a major plinian eruption with dacitic pyroclastic flows about 1900 years ago. Post-caldera eruptions, primarily from Marum and Benbow cones, have partially filled the caldera floor and produced lava flows that ponded on the caldera floor or overflowed through gaps in the caldera rim. Post-caldera eruptions have also formed a series of scoria cones and maars along a fissure system oriented ENE-WSW. Eruptions have apparently occurred almost yearly during historical time from cones within the caldera or from flank vents. However, from 1850 to 1950, reporting was mostly limited to extra-caldera eruptions that would have affected local populations.

Chikurachki, Paramushir Island (Russia)
50.324°N, 155.461°E, Elevation 1781 m

KVERT reported that satellite images showed no activity at Chikurachki after 19 February. The Aviation Color Code was lowered to Green on 26 February.

Geologic summary: Chikurachki, the highest volcano on Paramushir Island in the northern Kuriles, is actually a relatively small cone constructed on a high Pleistocene volcanic edifice. Oxidized basaltic-to-andesitic scoria deposits covering the upper part of the young cone give it a distinctive red color. Frequent basaltic plinian eruptions have occurred during the Holocene. Lava flows from 1781-m-high Chikurachki reached the sea and form capes on the NW coast; several young lava flows also emerge from beneath the scoria blanket on the eastern flank. The Tatarinov group of six volcanic centers is located immediately to the south of Chikurachki, and the Lomonosov cinder cone group, the source of an early Holocene lava flow that reached the saddle between it and Fuss Peak to the west, lies at the southern end of the N-S-trending Chikurachki-Tatarinov complex. In contrast to the frequently active Chikurachki, the Tatarinov volcanoes are extensively modified by erosion and have a more complex structure. Tephrochronology gives evidence of only one eruption in historical time from Tatarinov, although its southern cone contains a sulfur-encrusted crater with fumaroles that were active along the margin of a crater lake until 1959.

Fuego, Guatemala
14.473°N, 90.88°W, Elevation 3763 m

In a special notice, INSIVUMEH reported that an effusive eruption at Fuego that began on 28 February produced 300-400-m-high lava fountains. One lava flow traveled 1.6 km S down the Trinidad drainage and another traveled 600 m W down the Santa Teresa drainage. The eruption produced rumbling and train sounds audible up to 12 km away. Ash plumes rose 850-1,250 m above the crater and drifted 35 km W. Ashfall was reported in nearby areas including Panimache (8 km SW), Morelia (9 km SW), and Santa Sofía (12 km SW). During 28 February-1 March explosions generated ash plumes that rose an average of 650 m and drifted 9-10 km W. Incandescent material was ejected 150 m above the crater, and a small lava flow (400 m long) descended the Trinidad drainage. INSIVUMEH noted that the effusive phase had ended at 2156 on 1 March. Ash plumes from explosions rose 550-750 m and drifted 10 km W on 2 March and SW on 3 March.

Geologic summary: Volcán Fuego, one of Central America's most active volcanoes, is one of three large stratovolcanoes overlooking Guatemala's former capital, Antigua. The scarp of an older edifice, Meseta, lies between 3763-m-high Fuego and its twin volcano to the north, Acatenango. Construction of Meseta dates back to about 230,000 years and continued until the late Pleistocene or early Holocene. Collapse of Meseta may have produced the massive Escuintla debris-avalanche deposit, which extends about 50 km onto the Pacific coastal plain. Growth of the modern Fuego volcano followed, continuing the southward migration of volcanism that began at Acatenango. In contrast to the mostly andesitic Acatenango, eruptions at Fuego have become more mafic with time, and most historical activity has produced basaltic rocks. Frequent vigorous historical eruptions have been recorded since the onset of the Spanish era in 1524, and have produced major ashfalls, along with occasional pyroclastic flows and lava flows.

Popocatepetl, Mexico
19.023°N, 98.622°W, Elevation 5426 m

CENAPRED reported that a series of explosions at Popocatépetl from 2250 on 24 February to 0345 on 25 February was accompanied by periods of tremor andStrombolian activity which ejected incandescent material as far as 700 m onto the NE and SE flanks. Additional explosions (19) were detected on 25 February. Ashfall was reported in San Martín Texmelucan, San Matías Tlalancaleca, San Salvador el Verde, Santa Rita Tlahuapan, Tlaltenango, Huejotzingo, San Miguel Xoxtla, Domingo Arenas, Santa María Atexcac, and the Puebla airport. Explosions on 26 February ejected incandescent tephra 700 m away from the crater onto the N and NE flanks. Ashfall was noted in Domingo Arenas, San Martín Texmelucan, and Huejotzingo in the state of Puebla. The international airport in Huejotzingo suspended operations to clean up the ash. Steam, gas, and ash plumes drifted NE.

On 27 February explosions generated ash emissions and ejected incandescent tephra 300 m onto the flanks. Ashfall was reported in Huejotzingo, Domingo Arenas, Tlaltenango, San Andrés Cholula, and Puebla. During an overflight that same day, volcanologists observed dome number 55 which had grown and was filling the bottom of the inner crater. The dome was 250 m in diameter and at least 40 m thick, putting it about 60 m from the bottom of the main crater floor. The volume was an estimated 1.96 million cubic meters. The volcanologists also observed a small explosion that produced a 1.5-km-high ash plume.

Two separate series of explosions were detected on 28 February, and incandescent tephra was ejected 300 m onto the flanks. Steam-and-gas plumes rose from the crater during 1-2 March. Steam, gas, and ash plumes rose as high as 1.5 km on 3 March. Low-amplitude harmonic tremor and explosions were detected. Ash emissions drifted N. Incandescent tephra was ejected 100-300 m onto the N and NE flanks. The Alert Level remained at Yellow, Phase Two.

Geologic summary: Volcán Popocatépetl, whose name is the Aztec word for smoking mountain, towers to 5426 m 70 km SE of Mexico City to form North America's 2nd-highest volcano. The glacier-clad stratovolcano contains a steep-walled, 400 x 600 m wide crater. The generally symmetrical volcano is modified by the sharp-peaked Ventorrillo on the NW, a remnant of an earlier volcano. At least three previous major cones were destroyed by gravitational failure during the Pleistocene, producing massive debris-avalanche deposits covering broad areas to the south. The modern volcano was constructed south of the late-Pleistocene to Holocene El Fraile cone. Three major plinian eruptions, the most recent of which took place about 800 CE, have occurred from Popocatépetl since the mid Holocene, accompanied by pyroclastic flows and voluminous lahars that swept basins below the volcano. Frequent historical eruptions, first recorded in Aztec codices, have occurred since precolumbian time.

Sangay, Ecuador
2.005°S, 78.341°W, Elevation 5286 m

Based on a SIGMET notice of a pilot observation, the Washington VAAC reported that on 26 February an ash plume from Sangay rose to an altitude of 7.3 km (24,000 ft) a.s.l. Satellite images only detected an intermittent thermal anomaly. According to the VAAC, on 27 February IG reported a lava flow and a possible diffuse ash plume that rose to an altitude below 5.5 km (18,000 ft) a.s.l. within 15 km of the summit. On 2 March a local pilot observed an ash plume that rose to an altitude of 7.6 km (25,000 ft) a.s.l. On 3 March an ash plume rose to an estimated altitude of 5.2 km (17,000 ft) a.s.l. and drifted 13 km W.

Geologic summary: The isolated Sangay volcano, located east of the Andean crest, is the southernmost of Ecuador's volcanoes, and its most active. The dominantly andesitic volcano has been in frequent eruption for the past several centuries. The steep-sided, 5230-m-high glacier-covered volcano grew within horseshoe-shaped calderas of two previous edifices, which were destroyed by collapse to the east, producing large debris avalanches that reached the Amazonian lowlands. The modern edifice dates back to at least 14,000 years ago. It towers above the tropical jungle on the east side; on the other sides flat plains of ash have been sculpted by heavy rains into steep-walled canyons up to 600 m deep. The earliest report of a historical eruption was in 1628. More or less continuous eruptions were reported from 1728 until 1916, and again from 1934 to the present. The almost constant activity has caused frequent changes to the morphology of the summit crater complex.

Villarrica, Chile
39.42°S, 71.93°W, Elevation 2847 m

OVDAS-SERNAGEOMIN reported that on 28 February a significant increase in seismicity at Villarrica was detected along with Strombolian explosions andtephra ejected 1 km away. Seismicity continued to increase and on 2 March indicated that the lava lake level had risen. Strombolian explosions continued and ejected tephra as far as 600 m onto the flanks. Seismicity again increased significantly at 0230 on 3 March. The Alert Level was raised to Red (the highest level on a four-color scale). Strombolian activity intensified and became continuous, ejecting a large volume of material onto the flanks and producing a 1.5-km-tall lava fountain. Lava flows descended the flanks. The eruptive plume rose 6-8 km above the crater and drifted 400 km ENE. According to ONEMI about 3,600 people were evacuated from a 10-km-radius of the volcano. At 1500 ONEMI reported that seismicity was decreasing, and by 1800 was low. Only weak pulses of ashrose from the crater, and most evacuees had returned home.

Geologic summary: Glacier-clad Villarrica, one of Chile's most active volcanoes, rises above the lake and town of the same name. It is the westernmost of three large stratovolcanoes that trend perpendicular to the Andean chain. A 6-km wide caldera formed during the late Pleistocene. A 2-km-wide caldera that formed about 3500 years ago is located at the base of the presently active, dominantly basaltic to basaltic-andesitic cone at the NW margin of the Pleistocene caldera. More than 30 scoria cones and fissure vents dot Villarrica's flanks. Plinian eruptions and pyroclastic flows that have extended up to 20 km from the volcano have been produced during the Holocene. Lava flows up to 18 km long have issued from summit and flank vents. Historical eruptions, documented since 1558, have consisted largely of mild-to-moderate explosive activity with occasional lava effusion. Glaciers cover 40 sq km of the volcano, and lahars have damaged towns on its flanks.

Aira, Kyushu (Japan)
31.593°N, 130.657°E, Elevation 1117 m

JMA reported that eight explosions from Showa Crater at Aira Caldera’s Sakurajima volcano ejected tephra as far as 1,300 m during 23-27 February. An explosion on 24 February generated an ash plume that rose 3.3 km. Incandescence from the crater was visible at night on 25 and 27 February, and inflation continued to be detected. The Alert Level remained at 3 (on a scale of 1-5). The Tokyo VAAC reported that during 25-28 February and 2-3 March plumes rose to altitudes of 1.2-3.4 km (4,000-11,000 ft) a.s.l. and drifted N, NE, E, and SE.

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.

Bardarbunga, Iceland
64.63°N, 17.53°W, Elevation 2009 m

The Icelandic Met Office reported that the eruption at Bárdarbunga’s Holuhraun eruptive fissure, which began on 31 August 2014, had ended on 27 February; the Aviation Colour Code was lowered to Yellow. During an overflight scientists did not see any incandescence from the vents, although gas emissions persisted. Radar measurements showed that no increase in the extent of the lava field had been detected since mid-February.

Geologic summary: The large central volcano of Bárdarbunga lies beneath the NW part of the Vatnajökull icecap, NW of Grímsvötn volcano, and contains a subglacial 700-m-deep caldera. Related fissure systems include the Veidivötn and Trollagigar fissures, which extend about 100 km SW to near Torfajökull volcano and 50 km NE to near Askja volcano, respectively. Voluminous fissure eruptions, including one at Thjorsarhraun, which produced the largest known Holocene lava flow on Earth with a volume of more than 21 cu km, have occurred throughout the Holocene into historical time from the Veidivötn fissure system. The last major eruption of Veidivötn, in 1477, also produced a large tephra deposit. The subglacial Loki-Fögrufjöll volcanic system located SW of Bárdarbunga volcano is also part of the Bárdarbunga volcanic system and contains two subglacial ridges extending from the largely subglacial Hamarinn central volcano; the Loki ridge trends to the NE and the Fögrufjöll ridge to the SW. Jökulhlaups (glacier-outburst floods) from eruptions at Bárdarbunga potentially affect drainages in all directions.

Chirinkotan, Kuril Islands (Russia)
48.98°N, 153.48°E, Elevation 724 m

In a report from 4 March SVERT noted that weak steam-and-gas emissions from Chirinkotan were observed in January and February but that volcanic activity was not currently observed; the Aviation Color Code was lowered to Green.

Geologic summary: The small, mostly unvegetated 3-km-wide island of Chirinkotan occupies the far end of an E-W-trending volcanic chain that extends nearly 50 km west of the central part of the main Kuril Islands arc. Chirinkotan is the emergent summit of a volcano that rises 3000 m from the floor of the Kuril Basin. A small 1-km-wide caldera about 300-400 m deep is open to the SE. Lava flows from a cone within the breached crater reached the north shore of the island. Historical eruptions have been recorded at Chirinkotan since the 18th century. Fresh lava flows also descended the SE flank of Chirinkotan during an eruption in the 1880s that was observed by the English fur trader Captain Snow.

Chirpoi, Kuril Islands (Russia)
46.525°N, 150.875°E, Elevation 742 m

SVERT reported that satellite images over Snow, a volcano of Chirpoi, showed gas-and-steam emissions on 23 February and a thermal anomaly on 23 and 25 February. Cloud cover obscured views on other days during 23 February-2 March. The Aviation Color Code remained at Yellow.

Geologic summary: Chirpoi, a small island lying between the larger islands of Simushir and Urup, contains a half dozen volcanic edifices constructed within an 8-9 km wide, partially submerged caldera. The southern rim of the caldera is exposed on nearby Brat Chirpoev Island. The symmetrical Cherny volcano, which forms the 691 m high point of the island, erupted twice during the 18th and 19th centuries. The youngest volcano, Snow, originated between 1770 and 1810. It is composed almost entirely of lava flows, many of which have reached the sea on the southern coast. No historical eruptions are known from 742-m-high Brat Chirpoev, but its youthful morphology suggests recent strombolian activity.

Colima, Mexico
19.514°N, 103.62°W, Elevation 3850 m

Based on satellite images, Mexico City MWO, and a webcam, the Washington VAAC reported that during 25 February-3 March multiple gas-and-ash plumes per day from Colima rose to altitudes of 5.2-7.6 km (17,000-25,000 ft) a.s.l. and drifted in multiple directions. Ash drifted as far as 370 km SE (on 28 February). New thermal anomalies were identified on 28 February and continued through 2 March.

Geologic summary: The Colima volcanic complex is the most prominent volcanic center of the western Mexican Volcanic Belt. It consists of two southward-younging volcanoes, Nevado de Colima (the 4320 m high point of the complex) on the north and the 3850-m-high historically active Volcán de Colima at the south. A group of cinder cones of late-Pleistocene age is located on the floor of the Colima graben west and east of the Colima complex. Volcán de Colima (also known as Volcán Fuego) is a youthful stratovolcano constructed within a 5-km-wide caldera, breached to the south, that has been the source of large debris avalanches. Major slope failures have occurred repeatedly from both the Nevado and Colima cones, and have produced a thick apron of debris-avalanche deposits on three sides of the complex. Frequent historical eruptions date back to the 16th century. Occasional major explosive eruptions (most recently in 1913) have destroyed the summit and left a deep, steep-sided crater that was slowly refilled and then overtopped by lava dome growth.

Karymsky, Eastern Kamchatka (Russia)
54.049°N, 159.443°E, Elevation 1513 m

KVERT reported that during 20-27 February moderate seismicity at Karymsky was detected. Satellite images showed a thermal anomaly over the volcano on 21 and 24 February, and ash plumes drifting 254 km ENE on 23 February. 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, located immediately south. The caldera enclosing Karymsky formed about 7600-7700 radiocarbon years ago; construction of the 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, Elevation 1222 m

During 25 February-3 March HVO reported that Kilauea’s 27 June NE-trending lava flow continued to widen with several small breakouts across the interior and edges of the lobes, upslope of the leading front. These breakouts included a lobe extending to the N, which remained about 1.6 km upslope from Highway 130, and a lobe on the S side of the flow, about 870 m upslope of Malama Market. The most distal lobe of lava remained about 500 m above Highway 130, near police and fire stations. At Pu'u 'O'o Crater, glow emanated from several outgassing openings in the crater floor and minor lava flows within the crater were observed. During an overflight on 27 February volcanologists observed a few lava ponds in the vents. The circulating lava lake occasionally rose and fell in the deep pit within Halema'uma'u Crater. Gas emissions remained elevated.

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.

Klyuchevskoy, Central Kamchatka (Russia)
56.056°N, 160.642°E, Elevation 4754 m

KVERT reported that during 20-27 February a Strombolian and Vulcanian eruption at Klyuchevskoy continued. Incandescence at the summit was visible and bombs were ejected 150 m above the crater. Explosions generated ash plumes that rose to altitudes of 5-6 km (16,400-19,700 ft) a.s.l. Satellite images showed a daily, big, bright thermal anomaly over the volcano and ash plumes that drifted 430 km mainly NE, E, and SE. The Aviation Color Code remained at Orange.

Geologic summary: Klyuchevskoy (also spelled Kliuchevskoi) is Kamchatka's highest and most active volcano. Since its origin about 6000 years ago, the beautifully symmetrical, 4835-m-high basaltic stratovolcano has produced frequent moderate-volume explosive and effusive eruptions without major periods of inactivity. It rises above a saddle NE of sharp-peaked Kamen volcano and lies SE of the broad Ushkovsky massif. More than 100 flank eruptions have occurred during the past roughly 3000 years, with most lateral craters and cones occurring along radial fissures between the unconfined NE-to-SE flanks of the conical volcano between 500 m and 3600 m elevation. The morphology of the 700-m-wide summit crater has been frequently modified by historical eruptions, which have been recorded since the late-17th century. Historical eruptions have originated primarily from the summit crater, but have also included numerous major explosive and effusive eruptions from flank craters.

Nishinoshima, Japan
27.247°N, 140.874°E, Elevation 25 m

According to news articles, the eruption at Nishinoshima continued at least through 27 February. The Japan Coast Guard noted that the island had grown to about 2.46 square kilometers and the active cone was about 100 m tall. Explosions occurred several times per minute and ash-and-gas plumes rose 1.2 km. Steam plumes rose from areas where lava flows contacted sea water.

Geologic summary: The small island of Nishinoshima was recently enlarged when it was joined to several new islands that formed during an eruption in 1973-74. Water discoloration has been observed on several occasions since. The 700-m-wide island is the summit of a massive submarine volcano that has prominent satellitic peaks to the S, W, and NE. The summit of the southern cone rises to within 214 m of the sea surface 9 km SSE.

Reventador, Ecuador
0.077°S, 77.656°W, Elevation 3562 m

During 25 February-3 March IG reported moderate seismic activity including explosions, long-period earthquakes, harmonic tremor, and occasional tremor at Reventador; cloud cover often prevented visual observations. On 25 February a thermal anomaly was detected from the lava flow on the SW flank. On 27 February continuous emissions of gas and ash rose 1 km and drifted SW. A steam-and-ash plume rose 600 m and drifted W on 1 March.

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. It 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 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.

Sheveluch, Central Kamchatka (Russia)
56.653°N, 161.36°E, Elevation 3283 m

KVERT reported that during 20-27 February lava-dome extrusion onto Sheveluch’s N flank was accompanied by incandescence, hot block avalanches, andfumarolic activity. Strong explosions during 20-21, 24, and 26 February generated ash plumes that rose to altitudes of 6-7 km (19,700-23,000 ft) a.s.l. and drifted 580 km E and NE during 20-21 and 24-26 February. A thermal anomaly over the dome was detected daily. The Aviation Color Code remained at Orange. According to a news article ash caused a few flight cancellations in W Alaska on 28 February.

Geologic summary: The high, isolated massif of Sheveluch volcano (also spelled Shiveluch) rises above the lowlands NNE of the Kliuchevskaya volcano group. The 1300 cu km volcano 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 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.

Shishaldin, Fox Islands (USA)
54.756°N, 163.97°W, Elevation 2857 m

AVO reported that seismicity at Shishaldin continued to be elevated over background levels during 25 February-3 March. Elevated surface temperatures, sometimes that were highly elevated, were detected in satellite images almost daily. The webcam recorded minor degassing on 25 February and a low-level plume during 28 February-1 March. Low-level eruptive activity confined to the summit crater likely continued. 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, it 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. There are 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.

Zhupanovsky, Eastern Kamchatka (Russia)
53.589°N, 159.15°E, Elevation 2899 m

KVERT reported that a moderate explosive eruption at Zhupanovsky continued during 20-27 February. Satellite images detected a thermal anomaly over the volcano during 20-22 and 25-26 February. Ash clouds rose to altitudes of 3-3.5 km (10,000-11,500 ft) a.s.l. and drifted about 250 km E and SE. The Aviation Color Code remained at Orange.

Geologic summary: The Zhupanovsky volcanic massif consists of four overlapping stratovolcanoes along a WNW-trending ridge. The elongated volcanic complex was constructed within a Pliocene-early Pleistocene caldera whose rim is exposed only on the eastern side. Three of the stratovolcanoes were built during the Pleistocene, the fourth is Holocene in age and was the source of all of Zhupanovsky's historical eruptions. An early Holocene stage of frequent moderate and weak eruptions from 7000 to 5000 years before present (BP) was succeeded by a period of infrequent larger eruptions that produced pyroclastic flows. The last major eruption took place about 800-900 years BP. Historical eruptions have consisted of relatively minor explosions from the third cone.

Source: GVP