New activity/unrest was observed at 7 volcanoes from June 24 - 30, 2015. During the same period, ongoing activity was observed at 13 volcanoes.
New activity/unrest: Cereme, Western Java (Indonesia) | Cleveland, Chuginadak Island (USA) | Colo, Sulawesi (Indonesia) | Concepcion, Nicaragua | Hakoneyama, Honshu (Japan) | Raung, Eastern Java (Indonesia) | Sinabung, Indonesia.
Ongoing activity: Aira, Kyushu (Japan) | Colima, Mexico | Dukono, Halmahera (Indonesia) | Fuego, Guatemala | Karangetang, Siau Island (Indonesia) | Karymsky, Eastern Kamchatka (Russia) | Kilauea, Hawaiian Islands (USA) | Manam, Papua New Guinea | Nishinoshima, Japan | Sheveluch, Central Kamchatka (Russia) | Shishaldin, Fox Islands (USA) | Ubinas, Peru | Zhupanovsky, Eastern Kamchatka (Russia).
Cereme, Western Java (Indonesia)
6.892°S, 108.4°E, Summit elev. 3078 m
According to the Darwin VAAC a pilot observed a small "smoke" plume rising from Cereme on 24 June; ash was not identified in satellite images.
Geologic summary: The symmetrical stratovolcano Cereme, also known as Ciremai, is located closer to the northern coast than other central Java volcanoes. A steep-sided double crater elongated in an E-W direction caps 3078-m-high Gunung Cereme, which was constructed on the northern rim of the 4.5 x 5 km Geger Halang caldera. A large landslide deposit to the north may be associated with the origin of the caldera, although collapse may rather be due to a voluminous explosive eruption (Newhall and Dzurisin, 1988). Eruptions, relatively infrequent in historical time, have included explosive activity and lahars, primarily from the summit crater.
Cleveland, Chuginadak Island (USA)
52.825°N, 169.944°W, Summit elev. 1730 m
AVO reported that no significant activity was detected at Cleveland in seismic or infrasound data during 24-30 June. Elevated surface temperatures were detected during 28-30 June, and webcam images from 29 June showed fresh ash deposits at the summit. The Aviation Color Code remained at Yellow and the Volcano Alert Level remained at Advisory.
Geologic 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.
Colo, Sulawesi (Indonesia)
0.162°S, 121.601°E, Summit elev. 404 m
PVMBG reports that seismicity at Colo significantly increased on 8 June, particularly volcanic and shallow-volcanic earthquakes; 12 volcanic earthquakes were recorded on 22 June (previously, 1-5 events per day had been recorded), and there were 11 shallow volcanic earthquakes on 23 June (previously, 1-8 events per day had been recorded). On 24 June the Alert Level was raised to 2 (on a scale of 1-4). However, observers at the Colo Volcano Observation Post in the Wakai village did not see plumes during April-23 June. Residents and tourists were warned not to approach the volcano within a radius of 1.5 km.
Geologic summary: Colo volcano forms the isolated small island of Una Una in the middle of the Gulf of Tomini in northern Sulawesi. The broad, low volcano contains a 2-km-wide caldera with a small central cone. Only three eruptions have been recorded in historical time, but two of those caused widespread damage over much of the island. The last eruption, in 1983, produced pyroclastic flows that swept over most of the island shortly after all residents had been evacuated.
11.538°N, 85.622°W, Summit elev. 1700 m
INETER reported that gas explosions continued to be detected at Concepción; by 30 June a total of 2,417 explosions, 113 since 23 June, had been detected by the network since activity increased (date not specified).
Geologic summary: Volcán Concepción is one of Nicaragua's highest and most active volcanoes. The symmetrical basaltic-to-dacitic stratovolcano forms the NW half of the dumbbell-shaped island of Ometepe in Lake Nicaragua and is connected to neighboring Madera volcano by a narrow isthmus. A steep-walled summit crater is 250 m deep and has a higher western rim. N-S-trending fractures on the flanks of the volcano have produced chains of spatter cones, cinder cones, lava domes, and maars located on the NW, NE, SE, and southern sides extending in some cases down to Lake Nicaragua. Concepción was constructed above a basement of lake sediments, and the modern cone grew above a largely buried caldera, a small remnant of which forms a break in slope about halfway up the north flank. Frequent explosive eruptions during the past half century have increased the height of the summit significantly above that shown on current topographic maps and have kept the upper part of the volcano unvegetated.
Hakoneyama, Honshu (Japan)
35.233°N, 139.021°E, Summit elev. 1438 m
JMA reported that on 29 June scientists visiting Hakoneyama observed new fumaroles in a landslide-prone area, appearing after a possible landslide had occurred. Fresh sediment deposits within 2 km were possibly caused by the formation of the fumaroles. Seismicity began increasing at 1930, and a 5-minute-period of volcanic tremor began at 1932. At 1230 on 30 June a small-scale eruption occurred. The Alert Level was raised to 3 (on a 5-level scale).
Geologic summary: Hakoneyama volcano is truncated by two overlapping calderas, the largest of which is 10 x 11 km wide. The calderas were formed as a result of two major explosive eruptions about 180,000 and 49,000-60,000 years ago. Scenic Lake Ashi lies between the SW caldera wall and a half dozen post-caldera lava domes that were constructed along a SW-NE trend cutting through the center of the calderas. Dome growth occurred progressively to the south, and the largest and youngest of these, Kamiyama, forms the high point of Hakoneyama. The calderas are breached to the east by the Hayakawa canyon. A phreatic explosion about 3000 years ago was followed by collapse of the NW side of Kamiyama, damming the Hayakawa valley and creating Lake Ashi. The latest magmatic eruptive activity about 2900 years ago produced a pyroclastic flow and a lava dome in the explosion crater, although phreatic eruptions took place as recently as the 12-13th centuries CE. Seismic swarms have occurred during the 20th century. Lake Ashi, along with major thermal areas in the caldera, forms a popular resort area SW of Tokyo.
Raung, Eastern Java (Indonesia)
8.125°S, 114.042°E, Summit elev. 3332 m
PVMBG reported that, during times of clear weather during 1-28 June, white plumes were observed rising as high as 300 m above Raung's crater rim. Rumbling was frequently heard at the observation post. Seismic tremor sharply increased on 21 June, and crater incandescence was observed on 25 and 28 June. BNPB reported that increased activity on 28 June was characterized by Strombolian activity, roaring, ash plumes that rose 300 m, and a loud thumping sound heard 20 km away at 2000. Incandescence from the crater was clearly visible from the observation post in Banyuwangi. PVMBG raised the Alert Level to 3 (on a scale of 1-4) on 29 June, and reminded the public not to approach the crater within a 3-km radius.
Geologic summary: Raung, one of Java's most active volcanoes, is a massive stratovolcano in easternmost Java that was constructed SW of the rim of Ijen caldera. The 3332-m-high, unvegetated summit of Gunung Raung is truncated by a dramatic steep-walled, 2-km-wide caldera that has been the site of frequent historical eruptions. A prehistoric collapse of Gunung Gadung on the west flank produced a large debris avalanche that traveled 79 km from the volcano, reaching nearly to the Indian Ocean. Raung contains several centers constructed along a NE-SW line, with Gunung Suket and Gunung Gadung stratovolcanoes being located to the NE and west, respectively.
3.17°N, 98.392°E, Summit elev. 2460 m
PVMBG reported that foggy weather sometimes prevented visual observations of Sinabung during 22-29 June. White plumes rose as high as 500 m above the crater, and lava flows on the flanks were incandescent as far as 3 km S and SE. Multiple pyroclastic flows per day during 22-26 and 28 June traveled 2.5-4 km down the flanks from the SSE to the SE. One pyroclastic flow was observed on 27 June. Ash plumes rose generally 3.5 km on most days, drifting E, SE, and S, although an ash plume rose as high as 5 km on 25 June. Seismicity consisted of avalanche signals, low-frequency and hybrid events, tremor, tectonic events, and volcanic earthquakes; RSAM values increased due to an increase of avalanche signals. Deformation data showed a trend of inflation. The Alert Level remained at 4 (on a scale of 1-4), indicating that people within 7 km of the volcano on the SSE sector, and within 6 km in the ESE sector, should evacuate.
Geologic 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.
Aira, Kyushu (Japan)
31.593°N, 130.657°E, Summit elev. 1117 m
JMA reported 26 explosions during 22-29 June from Showa Crater at Aira Caldera’s Sakurajima volcano, some that ejected tephra as far as 1,300 m, and incandescence from the crater that was visible during 22-23 and 27 June. A small-scale eruption occurred from Minami-Dake Crater on 22 June. The Alert Level remained at 3 (on a 5-level scale).
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.
19.514°N, 103.62°W, Summit elev. 3850 m
The Washington VAAC reported that an ash-and-gas plume from an explosion at Colima was recorded by the webcam on 24 June; weather clouds prevented views of the volcano.
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.
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 during 27-28 June ash plumes from Dukono rose to an altitude of 1.8 km (6,000 ft) a.s.l. and drifted 55-75 km NE.
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. 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.
14.473°N, 90.88°W, Summit elev. 3763 m
In a special report from 28 June at 2100, INSIVUMEH reported that activity at Fuego had been changing during the previous few hours, characterized by 4-5 explosions per hour and ash plumes rising 850 m. During 28-30 June ash plumes drifted W, causing ashfall in areas downwind. Shock waves from the explosions vibrated structures in areas including Panimache and Panimache II (8 km SW), Morelia (9 km SW), Santa Sofía (12 km SW), and Sangre de Cristo (8 km WSW). Block avalanches descended the flanks. Rumbling was audible as far as 25 km away. During 29-30 June a 300-m-long lava flow was visible in the Las Lajas drainage on the SE flank.
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.
Karangetang, Siau Island (Indonesia)
2.78°N, 125.4°E, Summit elev. 1784 m
PVMBG reported that on 18 June a lahar in Karangetang’s Batuawang drainage (E) was 25 cm thick, carried boulders, and covered a 100-m section of roadway. The lahar also damaged or destroyed four homes. Based on observations conducted at the Karangetang Volcano Observation Post in the village of Salili, white plumes rose as high as 150 m above the main crater and 25 m above Crater II during 22-29 June. Incandescence from the lava dome was observed at night. Lava flowed from the S part of the dome; incandescent avalanches from the front the lava flow traveled as far as 2.3 km towards Batuawang and Kahetang drainages (E). Seismicity was dominated by signals characteristic of avalanches, and indicated that activity continued to be high. The Alert Level remained at 3 (on a scale of 1-4); visitors and residents were warned not to approach Karangetang within a 4-km radius.
Geologic summary: Karangetang (Api Siau) volcano lies at the northern end of the island of Siau, north of Sulawesi. The 1784-m-high stratovolcano contains five summit craters along a N-S line. Karangetang is one of Indonesia's most active volcanoes, with more than 40 eruptions recorded since 1675 and many additional small eruptions that were not documented in the historical record (Catalog of Active Volcanoes of the World: Neumann van Padang, 1951). Twentieth-century eruptions have included frequent explosive activity sometimes accompanied by pyroclastic flows and lahars. Lava dome growth has occurred in the summit craters; collapse of lava flow fronts has also produced pyroclastic flows.
Karymsky, Eastern Kamchatka (Russia)
54.049°N, 159.443°E, Summit elev. 1513 m
KVERT reported that explosive activity at Karymsky likely continued during 19-26 June; weather clouds obscured views of the volcano. 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, Summit elev. 1222 m
HVO reported that seismicity beneath Kilauea's summit and upper East Rift Zone was at background levels during 24-30 June. The lava lake continued to be active in the deep pit within the Overlook vent, exhibiting vigorous spattering. The June 27th NE-trending lava flow continued to be active with surface flows within 8 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.
Manam, Papua New Guinea
4.08°S, 145.037°E, Summit elev. 1807 m
Based on observations of satellite imagery and wind data analyses, the Darwin VAAC reported that during 28-30 June ash plumes from Manam rose to altitudes of 1.8-3 km (6,000-10,000 ft) a.s.l. and drifted as far as 75 km NE.
Geologic summary: The 10-km-wide island of Manam, lying 13 km off the northern coast of mainland Papua New Guinea, is one of the country's most active volcanoes. Four large radial valleys extend from the unvegetated summit of the conical 1807-m-high basaltic-andesitic stratovolcano to its lower flanks. These "avalanche valleys" channel lava flows and pyroclastic avalanches that have sometimes reached the coast. Five small satellitic centers are located near the island's shoreline on the northern, southern, and western sides. Two summit craters are present; both are active, although most historical eruptions have originated from the southern crater, concentrating eruptive products during much of the past century into the SE valley. Frequent historical eruptions, typically of mild-to-moderate scale, have been recorded since 1616. Occasional larger eruptions have produced pyroclastic flows and lava flows that reached flat-lying coastal areas and entered the sea, sometimes impacting populated areas.
27.247°N, 140.874°E, Summit elev. 25 m
According to NASA's Earth Observatory, a satellite image of Nishinoshima acquired on 21 June showed a sulfur dioxide-and-steam plume rising from the 2.45-square-kilometer island and drifting NE. Hot spots from lava that had emerged from lava tubes were visible on a lava delta at the SE part of the island.
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.
Sheveluch, Central Kamchatka (Russia)
56.653°N, 161.36°E, Summit elev. 3283 m
KVERT reported that during 19-26 June lava-dome extrusion onto Sheveluch’s N flank was accompanied by fumarolic activity. Satellite images showed a thermal anomaly over the volcano during 23-24 June; weather clouds obscured the volcano on the other days. The Aviation Color Code remained at Orange.
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, Summit elev. 2857 m
AVO reported that seismicity at Shishaldin continued to be elevated over background levels 24-30 June, indicating that low-level eruptive activity confined to the summit crater likely continued. Elevated surface temperatures were periodically detected in satellite images. Webcam images showed ash deposits around the summit crater rim on 29 and 30 June. 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.
16.355°S, 70.903°W, Summit elev. 5672 m
Instituto Geofísico del Perú (IGP) Observatorio Volcanológico del Sur (OVS) reported that during 23-29 June seismic tremor at Ubinas, often associated with emissions, slightly increased compared to the previous week. Ash-and-gas plumes rose as high as 3 km above the crater base, drifting in multiple directions, and four explosions were detected during 24-27 June.
Geologic summary: A small, 1.4-km-wide caldera cuts the top of Ubinas, Peru's most active volcano, giving it a truncated appearance. It 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 was followed by construction of Ubinas II 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 about 3700 years ago extend 10 km from the volcano. Widespread plinian pumice-fall deposits include one of Holocene age about 1000 years ago. Holocene lava flows are visible on the flanks, but historical activity, documented since the 16th century, has consisted of intermittent minor-to-moderate explosive eruptions.
Zhupanovsky, Eastern Kamchatka (Russia)
53.589°N, 159.15°E, Summit elev. 2899 m
KVERT reported that explosive activity at Zhupanovsky probably continued during 19-26 June; weather clouds obscured views of the volcano. 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.