New activity/unrest was observed at 5 volcanoes between June 1 and 7, 2016. During the same period, ongoing activity was observed at 15 volcanoes.
New activity/unrest: Bristol Island, South Sandwich Islands (UK) | Kerinci, Indonesia | Santa Maria, Guatemala | Suretamatai, Banks Islands (Vanuatu) | Turrialba, Costa Rica.
Ongoing activity: Aira, Kyushu (Japan) | Alaid, Kuril Islands (Russia) | Ambrym, Vanuatu | Bagana, Bougainville (Papua New Guinea) | Cleveland, Chuginadak Island (USA) | Colima, Mexico | Dukono, Halmahera (Indonesia) | Kilauea, Hawaiian Islands (USA) | Klyuchevskoy, Central Kamchatka (Russia) | Popocatepetl, Mexico | San Miguel, El Salvador | Sheveluch, Central Kamchatka (Russia) | Sinabung, Indonesia | Tengger Caldera, Eastern Java (Indonesia) | Yasur, Vanuatu.
Bristol Island, South Sandwich Islands (UK)
59.017°S, 26.533°W, Summit elev. 1100 m
The Buenos Aires VAAC reported that weather clouds mostly prevented satellite observations of Bristol Island's Mt. Sourabaya during 1-6 June, though a thermal anomaly was detected during 1-2 and 5-6 June.
Geological summary: The 9 x 10 km Bristol Island near the southern end of the South Sandwich arc lies across Fortser's Passage from the Southern Thule Islands and forms one of the largest islands of the chain. Largely glacier-covered, it contains a horseshoe-shaped ridge at the interior extending northward from the highest peak, 1100-m-high Mount Darnley. A steep-sided flank cone or lava dome, Havfruen Peak, is located on the east side, and a young crater and fissure are on the west flank. Three large sea stacks lying off Turmoil Point at the western tip of the island may be remnants of an older now-eroded volcanic center. Both summit and flank vents have been active during historical time. The latest eruption, during 1956, originated from the west-flank crater, and deposited cinder over the icecap. The extensive icecap and the difficulty of landing make it the least explored of the South Sandwich Islands.
1.697°S, 101.264°E, Summit elev. 3800 m
Based on satellite data and information from PVMBG, the Darwin VAAC reported that during 4-6 June ash plumes from Kerinci rose to altitudes of 4.3-4.6 km (14,000-15,000 ft) a.s.l. and drifted NW and N.
Geological summary: The 3800-m-high Gunung Kerinci in central Sumatra forms Indonesia's highest volcano and is one of the most active in Sumatra. Kerinci is capped by an unvegetated young summit cone that was constructed NE of an older crater remnant. The volcano contains a deep 600-m-wide summit crater often partially filled by a small crater lake that lies on the NE crater floor, opposite the SW-rim summit of Kerinci. The massive 13 x 25 km wide volcano towers 2400-3300 m above surrounding plains and is elongated in a N-S direction. The frequently active Gunung Kerinci has been the source of numerous moderate explosive eruptions since its first recorded eruption in 1838.
Santa Maria, Guatemala
14.756°N, 91.552°W, Summit elev. 3772 m
In a special report posted on 1 June, INSIVUMEH reported that activity at Santa María's Santiaguito lava-dome complex remained high. Two strong explosions generated ash plumes that rose as high as 2.4 km above the complex and drifted 30-40 km NE, SE, and SW. During 3-4 June gas-and-ash plumes rose 300 m.
Geological 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 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.
Suretamatai, Banks Islands (Vanuatu)
13.8°S, 167.47°E, Summit elev. 921 m
On 27 May the Vanuatu Geohazards Observatory stated that the Alert Level for Suretamatai was increased to 1 (on a scale of 0-4) because of a change in activity. VGO reminded residents and tourists that areas around the volcano and along the Sulfur River (E flank) were high-risk zones due to potential impacts from volcanic gas emissions.
Geological summary: Suretamatai volcano forms much of Vanua Lava Island, one of the largest of Vanuatu's Banks Islands. The younger lavas of 921-m-high Suretamatai (also known as Soritimeat) volcano overlie a number of small older stratovolcanoes that form the island. In contrast to other large volcanoes of Vanuatu, the dominantly basaltic-to-andesitic Suretamatai does not contain a youthful summit caldera. A chain of small stratovolcanoes, oriented along a NNE-SSW line, gives the low-angle volcano an irregular profile. The youngest cone, near the northern end of the chain, is the largest and contains a lake of variable depth within its 900-m-wide, 100-m-deep summit crater. Historical activity, beginning during the 19th century, has been restricted to moderate explosive eruptions.
Turrialba, Costa Rica
10.025°N, 83.767°W, Summit elev. 3340 m
OVSICORI-UNA reported that activity at Turrialba had declined overall since 27 May, though seismicity continued to be dominated by long-period earthquakes and small low-frequency volcanic earthquakes. A small explosion at 0516 on 1 June generated an ash plume that rose 300 m above the vent and, based on wind dispersion models, likely drifted NW. Some residents of Valle Central reported ashfall. Continuous spasmodic tremor that began at 2240 was associated with ash emissions that rose as high as 1 km and drifted N. At 0037 on 2 June an explosion was followed by high-amplitude spasmodic tremor and a dense ash-rich plume that rose 1 km and drifted NNW. Ash emissions continued; at 0520 and 0600 ash plumes rose as high as 2 km and drifted NW, N, and NE. Tremor amplitude decreased at 1240. Afternoon clouds prevented observations of ash emissions. Ashfall was reported in several neighborhoods in San José, including San Rafael de Moravia (31 km WSW), Sabana (38 km WSW), and in Limón, including Buenos Aires (17 km N), and Pococí (45 km N). During 2-3 June ash emissions were sometimes observed rising as high as 1 km and drifted N and NE. Ashfall in areas of Limón continued to be reported. Tremor amplitude began to decline at 0621 on 3 June, and then further declined to low levels at 0330 on 4 June. At dawn on 4 June plumes of water vapor and gas rose 500 m. Degassing and seismicity remained low through 7 June.
Geological summary: Turrialba, the easternmost of Costa Rica's Holocene volcanoes, is a large vegetated basaltic-to-dacitic stratovolcano located across a broad saddle NE of Irazú volcano overlooking the city of Cartago. The massive 3340-m-high Turrialba is exceeded in height only by Irazú, covers an area of 500 sq km, and is one of Costa Rica's most voluminous volcanoes. Three well-defined craters occur at the upper SW end of a broad 800 x 2200 m summit depression that is breached to the NE. Most activity originated from the summit vent complex, but two pyroclastic cones are located on the SW flank. Five major explosive eruptions have occurred during the past 3500 years. A series of explosive eruptions during the 19th century were sometimes accompanied by pyroclastic flows. Fumarolic activity continues at the central and SW summit craters.
Aira, Kyushu (Japan)
31.593°N, 130.657°E, Summit elev. 1117 m
JMA reported that on 3 June explosions at Showa Crater (at Aira Caldera’s Sakurajima volcano) generated an ash plume that rose 1.3 km above the crater rim, and a small pyroclastic flow that traveled 400 m SE. Tephra was ejected 800 m from the crater. A small-scale explosion occurred at Minamidake summit crater that same day; an ash plume rose 1.5 km above the crater rim. The Alert Level remained at 3 (on a 5-level scale).
Geological 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.
Alaid, Kuril Islands (Russia)
50.861°N, 155.565°E, Summit elev. 2285 m
KVERT reported that moderate activity at Alaid continued during 27 May-3 June. Satellite images showed a thermal anomaly over the volcano on 29 May. The Aviation Color Code remained at Orange (the second highest level on a four-color scale).
Geological summary: The highest and northernmost volcano of the Kuril Islands, 2285-m-high Alaid is a symmetrical stratovolcano when viewed from the north, but has a 1.5-km-wide summit crater that is breached widely to the south. Alaid is the northernmost of a chain of volcanoes constructed west of the main Kuril archipelago and rises 3000 m from the floor of the Sea of Okhotsk. Numerous pyroclastic cones dot the lower flanks of basaltic to basaltic-andesite Alaid volcano, particularly on the NW and SE sides, including an offshore cone formed during the 1933-34 eruption. Strong explosive eruptions have occurred from the summit crater beginning in the 18th century. Reports of eruptions in 1770, 1789, 1821, 1829, 1843, 1848, and 1858 were considered incorrect by Gorshkov (1970). Explosive eruptions in 1790 and 1981 were among the largest in the Kuril Islands during historical time.
16.25°S, 168.12°E, Summit elev. 1334 m
On 27 May the Vanuatu Geohazards Observatory issued a statement reminding residents and visitors that Ambrym remained active; the Alert Level remained at 2 (on a 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.
Geological 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.
Bagana, Bougainville (Papua New Guinea)
6.137°S, 155.196°E, Summit elev. 1855 m
Based on analyses of satellite imagery and model data, the Darwin VAAC reported that on 2 June ash plumes from Bagana rose to an altitude of 2.1 km (7,000 ft) a.s.l. and drifted 75 km in multiple directions.
Geological summary: Bagana volcano, occupying a remote portion of central Bougainville Island, is one of Melanesia's youngest and most active volcanoes. This massive symmetrical, roughly 1850-m-high cone was largely constructed by an accumulation of viscous andesitic lava flows. The entire edifice could have been constructed in about 300 years at its present rate of lava production. Eruptive activity is frequent and 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. Satellite thermal measurements indicate a continuous eruption from before February 2000 through at least late August 2014.
Cleveland, Chuginadak Island (USA)
52.825°N, 169.944°W, Summit elev. 1730 m
AVO reported that seismic activity at Cleveland had remained low since explosions were detected in infrasound (pressure sensor) and seismic data on 5 and 10 May. No significant activity had been observed since satellite data confirmed the eruption of a small-volume lava dome within the summit crater on 18 May; weakly elevated surface temperatures detected during 2-3 June were consistent with cooling lava. On 3 June AVO lowered the Level of Concern Color Code to Yellow and the Volcano Alert Level was lowered to Advisory.
Geological summary: Beautifully symmetrical Mount Cleveland stratovolcano is situated at the western end of the uninhabited, dumbbell-shaped Chuginadak Island. It lies SE across Carlisle Pass strait from Carlisle volcano and NE across Chuginadak Pass strait from Herbert volcano. Cleveland is joined to the rest of Chuginadak Island by a low isthmus. The 1730-m-high Mount Cleveland is the highest of the Islands of the Four Mountains group and is one of the most active of the Aleutian Islands. The native name for Mount Cleveland, Chuginadak, refers to the Aleut goddess of fire, who was thought to reside on the volcano. Numerous large lava flows descend the steep-sided flanks. It is possible that some 18th-to-19th century eruptions attributed to Carlisle should be ascribed to Cleveland (Miller et al., 1998). In 1944 Cleveland produced the only known fatality from an Aleutian eruption. Recent eruptions have been characterized by short-lived explosive ash emissions, at times accompanied by lava fountaining and lava flows down the flanks.
19.514°N, 103.62°W, Summit elev. 3850 m
Based on satellite images and wind data, the Washington VAAC reported that on 3 June an ash plume from Colima rose to an altitude of 5.2 km (17,000 ft) a.s.l. and drifted SW.
Geological 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.
Dukono, Halmahera (Indonesia)
1.693°N, 127.894°E, Summit elev. 1229 m
Based on analyses of satellite imagery and wind data, the Darwin VAAC reported that during 1 and 3-7 June ash plumes from Dukono rose to altitudes of 2.1-2.4 km (7,000-8,000 ft) a.s.l. and drifted over 55 km in multiple directions.
Geological 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. This complex volcano presents a broad, low profile with multiple summit peaks and overlapping craters. Malupang Wariang, 1 km SW of the summit crater complex, contains a 700 x 570 m crater that has also been active during historical time.
Kilauea, Hawaiian Islands (USA)
19.421°N, 155.287°W, Summit elev. 1222 m
HVO reported that during 1-7 June the lava lake continued to rise and fall, circulate, and spatter in Kilauea's Overlook vent. Two new flows from Pu'u 'O'o Crater's N and E flanks, which began on 24 May, continued to be active within 1.3 km of their respective vents. The June 27th NE-trending lava flow continued to be active within 5.4 km NE of Pu'u 'O'o Crater.
Geological 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 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, Summit elev. 4754 m
KVERT reported that a Strombolian eruption at Klyuchevskoy continued during 27 May-3 June. Satellite and video data showed a lava flow effusing on the SE flank, down the Apakhonchich drainage. Satellite images showed an intense daily thermal anomaly over the volcano. The Aviation Color Code was raised to Orange.
Geological 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.
19.023°N, 98.622°W, Summit elev. 5426 m
During 1-7 June there were 94-251 daily emissions from Popocatépetl and as many as four explosions detected daily; some emissions corresponded with increased crater incandescence at night. A series of explosions detected during 1135-2230 on 4 June generated gas-and-steam emissions with minor amounts of ash that rose 1.5 km above the crater and drifted ENE. Some of the explosions ejected incandescent tephra 300 m onto the NE flanks. An explosion on 5 June generated an ash plume that rose 1.5 km and drifted E. Incandescent tephra was ejected 1 km onto the N flank. Between 0354 and 0824 on 6 June continuous explosions formed plumes that rose 1 km and drifted NE. The Alert Level remained at Yellow, Phase Two.
Geological 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.
San Miguel, El Salvador
13.434°N, 88.269°W, Summit elev. 2130 m
SNET reported that between 1304 and 1430 on 31 May seismic signals at San Miguel increased, and indicated rock fracturing at depth and possible gas-and-ash emissions. Though weather clouds partially covered the volcano, the webcam recorded some pulses of gas emissions. Seismicity decreased the next day.
Geological 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, 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.
Sheveluch, Central Kamchatka (Russia)
56.653°N, 161.36°E, Summit elev. 3283 m
KVERT reported that during 27 May-3 June lava-dome extrusion onto Sheveluch’s N flank was accompanied by strong fumarolic activity, dome incandescence, ash explosions, and hot avalanches. Satellite images showed an intense thermal anomaly over the dome during 26-29 May. The Aviation Color Code remained at Orange.
Geological 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.
3.17°N, 98.392°E, Summit elev. 2460 m
Based on satellite images and information from PVMBG, the Darwin VAAC reported that during 5-7 June ash plumes from Sinabung rose to altitudes of 3.3-3.9 km (11000-13,000 ft) a.s.l. and drifted SW.
Geological summary: Gunung Sinabung is a Pleistocene-to-Holocene stratovolcano with many lava flows on its flanks. The migration of summit vents along a N-S line gives the summit crater complex an elongated form. The youngest crater of this conical, 2460-m-high andesitic-to-dacitic volcano is at the southern end of the four overlapping summit craters. An unconfirmed eruption was noted in 1881, and solfataric activity was seen at the summit and upper flanks in 1912. No confirmed historical eruptions were recorded prior to explosive eruptions during August-September 2010 that produced ash plumes to 5 km above the summit.
Tengger Caldera, Eastern Java (Indonesia)
7.942°S, 112.95°E, Summit elev. 2329 m
Based on satellite images, wind data, and information from PVMBG, the Darwin VAAC reported that during 1-3 June ash plumes from Tengger Caldera's Bromo cone rose to an altitude of 3 km (10,000 ft) a.s.l. and drifted as far as 65 km N and NW.
Geological summary: The 16-km-wide Tengger caldera is located at the northern end of a volcanic massif extending from Semeru volcano. The massive volcanic complex dates back to about 820,000 years ago and consists of five overlapping stratovolcanoes, each truncated by a caldera. Lava domes, pyroclastic cones, and a maar occupy the flanks of the massif. The Ngadisari caldera at the NE end of the complex formed about 150,000 years ago and is now drained through the Sapikerep valley. The most recent of the calderas is the 9 x 10 km wide Sandsea caldera at the SW end of the complex, which formed incrementally during the late Pleistocene and early Holocene. An overlapping cluster of post-caldera cones was constructed on the floor of the Sandsea caldera within the past several thousand years. The youngest of these is Bromo, one of Java's most active and most frequently visited volcanoes.
19.53°S, 169.442°E, Summit elev. 361 m
On 27 May the Vanuatu Geohazards Observatory stated that the Alert Level for Yasur remained at 2 (on a scale of 0-4) and that explosions continued to be intense. VGO reminded residents and tourists that hazardous areas were near and around the volcanic crater, and that volcanic ash and gas could reach areas impacted by trade winds.
Geological summary: Yasur, the best-known and most frequently visited of the Vanuatu volcanoes, has been in more-or-less continuous strombolian and vulcanian activity since Captain Cook observed ash eruptions in 1774. This style of activity may have continued for the past 800 years. Located at the SE tip of Tanna Island, this mostly unvegetated pyroclastic cone has a nearly circular, 400-m-wide summit crater. Yasur is largely contained within the small Yenkahe caldera and is the youngest of a group of Holocene volcanic centers constructed over the down-dropped NE flank of the Pleistocene Tukosmeru volcano. The Yenkahe horst is located within the Siwi ring fracture, a 4-km-wide, horseshoe-shaped caldera associated with eruption of the andesitic Siwi pyroclastic sequence. Active tectonism along the Yenkahe horst accompanying eruptions has raised Port Resolution harbor more than 20 m during the past century.