New activity/unrest was reported for 4 volcanoes from January 22 to 28, 2020. During the same period, ongoing activity was reported for 14 volcanoes.
New activity/unrest: Fernandina, Ecuador | Kuchinoerabujima, Ryukyu Islands (Japan) | Reykjanes, Iceland | Taal, Luzon (Philippines).
Ongoing activity: Aira, Kyushu (Japan) | Dukono, Halmahera (Indonesia) | Ebeko, Paramushir Island (Russia) | Etna, Sicily (Italy) | Karangetang, Siau Island (Indonesia) | Kerinci, Indonesia | Klyuchevskoy, Central Kamchatka (Russia) | Nishinoshima, Japan | Sangeang Api, Indonesia | Semeru, Eastern Java (Indonesia) | Sheveluch, Central Kamchatka (Russia) | Shishaldin, Fox Islands (USA) | Suwanosejima, Ryukyu Islands (Japan) | Villarrica, Chile.
0.37°S, 91.55°W, Summit elev. 1476 m
A reported from IG on 23 January noted that seismicity increased after the approximately nine-hour long 12 January eruption at Fernandina, characterized by sporadic earthquakes with magnitudes greater than 3 and small swarms. The strongest earthquake was a M 4.2 recorded on 21 January. Most of the earthquakes were shallow though occasionally some were located at depths greater than 10 km. Deformation of about 35 cm was detected around the fissures that produced the lava flows. The lava flows emitted on 12 January covered an approximate area of 3.8 square kilometers; no new thermal anomalies nor gas emissions have been recorded since the eruption.
Geological summary: Fernandina, the most active of Galápagos volcanoes and the one closest to the Galápagos mantle plume, is a basaltic shield volcano with a deep 5 x 6.5 km summit caldera. The volcano displays the classic "overturned soup bowl" profile of Galápagos shield volcanoes. Its caldera is elongated in a NW-SE direction and formed during several episodes of collapse. Circumferential fissures surround the caldera and were instrumental in growth of the volcano. Reporting has been poor in this uninhabited western end of the archipelago, and even a 1981 eruption was not witnessed at the time. In 1968 the caldera floor dropped 350 m following a major explosive eruption. Subsequent eruptions, mostly from vents located on or near the caldera boundary faults, have produced lava flows inside the caldera as well as those in 1995 that reached the coast from a SW-flank vent. Collapse of a nearly 1 km3 section of the east caldera wall during an eruption in 1988 produced a debris-avalanche deposit that covered much of the caldera floor and absorbed the caldera lake.
Kuchinoerabujima, Ryukyu Islands (Japan)
30.443°N, 130.217°E, Summit elev. 657 m
Very small eruptive events recorded at Kuchinoerabujima on 20, 23, and 24 January produced grayish-white plumes that rose 500 m above the crater rim. Ashfall 2 km NE of the crater was confirmed during aerial observations on 23 January. The number of volcanic earthquakes increased during 25-26 January. An eruptive event was recorded at 0148 on 27 January, though weather clouds prevented visual confirmation; volcanic tremor, changes in tilt data, and infrasound signals accompanied the event. Sulfur dioxide gas emissions were 200-1,000 tons per day during 20-27 January; JMA characterized emissions of 600-1,000 tons per day as high.
Geological summary: A group of young stratovolcanoes forms the eastern end of the irregularly shaped island of Kuchinoerabujima in the northern Ryukyu Islands, 15 km W of Yakushima. The Furudake, Shindake, and Noikeyama cones were erupted from south to north, respectively, forming a composite cone with multiple craters. The youngest cone, centrally-located Shindake, formed after the NW side of Furudake was breached by an explosion. All historical eruptions have occurred from Shindake, although a lava flow from the S flank of Furudake that reached the coast has a very fresh morphology. Frequent explosive eruptions have taken place from Shindake since 1840; the largest of these was in December 1933. Several villages on the 4 x 12 km island are located within a few kilometers of the active crater and have suffered damage from eruptions.
63.85°N, 22.566°W, Summit elev. 140 m
IMO reported possible magma accumulation beneath Reykjanes, centered along the plate boundary below the Svartsengi fissure system, just W of Thorbjorn. Deformation began on 21 January and was unusually rapid, with the rate of inflation occurring at 3-4 mm per day (3 cm total by 29 January), as detected by InSAR and continuous GPS data. Magma accumulation, if that was causing the inflation, was small with an estimate volume of 1 million cubic meters, at 3-5 km depth. Deformation on the Reykjanes peninsula had been measured for three decades with no previously comparable signals.
An earthquake swarm accompanied the deformation, just E of the center of the inflation. The largest earthquakes were M 3.6 and 3.7, recorded on 22 January, and felt widely on the Reykjanes peninsula and all the way to Borgarnes region. Earthquake swarms are relatively common, though coupled with deformation caused IMO to raise the Aviation Code to Yellow on 26 January. The swarm was declining by 26 January. On 29 January IMO stated that data showed continuing uplift and the earthquake swarm was ongoing.
Geological summary: The Reykjanes volcanic system at the SW tip of the Reykjanes Peninsula, where the Mid-Atlantic Ridge rises above sea level, comprises a broad area of postglacial basaltic crater rows and small shield volcanoes. The submarine Reykjaneshryggur volcanic system is contiguous with and is considered part of the Reykjanes volcanic system, which is the westernmost of a series of four closely-spaced en-echelon fissure systems that extend diagonally across the Reykjanes Peninsula. Most of the subaerial part of the system (also known as the Reykjanes/Svartsengi volcanic system) is covered by Holocene lavas. Subaerial eruptions have occurred in historical time during the 13th century at several locations on the NE-SW-trending fissure system, and numerous submarine eruptions dating back to the 12th century have been observed during historical time, some of which have formed ephemeral islands. Basaltic rocks of probable Holocene age have been recovered during dredging operations, and tephra deposits from earlier Holocene eruptions are preserved on the nearby Reykjanes Peninsula.
Taal, Luzon (Philippines)
14.002°N, 120.993°E, Summit elev. 311 m
PHIVOLCS reported that white steam-laden plumes rose as high as 800 m above Taal’s main vent during 22-28 January and drifted SW and NE; ash emissions ceased around 0500 on 22 January. Remobilized ash drifted SW on 22 January due to strong low winds, affecting the towns of Lemery (16 km SW) and Agoncillo, and rose as high as 5.8 km (19,000 ft) a.s.l. as reported by pilots.
PHIVOLCS stated that since the 12-13 January phreatomagmatic eruption activity has generally weakened. Both the number and magnitude of volcanic earthquakes declined; by 21 January hybrid earthquakes had ceased and both the number and magnitude of low-frequency events had diminished. GPS data had recorded a sudden widening of Taal Caldera by ~1 m, uplift of the NW sector by ~20 cm, and subsidence of the SW part of Volcano Island by ~1 m just after the main eruption phase. The rate of the deformation patterns was smaller during 15-22 January, and generally corroborated by field observations; Taal Lake had receded about 30 cm by 25 January but about 2.5 m of lakewater recession (due to uplift) was observed around the SW portion of the lake, near the Pansipit River Valley where ground cracking had been reported. The Alert Level was lowered to 3 (on a scale of 0-5) on 26 January and PHIVOLCS recommended no entry onto Volcano Island and Taal Lake, nor into towns W of the island within a 7-km radius. Sulfur dioxide emissions were low at 140 tonnes per day on 22 January but averaged around 250 tonnes per day through 26 January; emissions were 87 tonnes per day on 27 January and below detectable limits the next day. According to the Disaster Response Operations Monitoring and Information Center (DROMIC) there were a total of 125,178 people in 497 evacuation centers as of 2020 on 28 January.
Geological summary: Taal is one of the most active volcanoes in the Philippines and has produced some of its most powerful historical eruptions. Though not topographically prominent, its prehistorical eruptions have greatly changed the landscape of SW Luzon. The 15 x 20 km Talisay (Taal) caldera is largely filled by Lake Taal, whose 267 km2 surface lies only 3 m above sea level. The maximum depth of the lake is 160 m, and several eruptive centers lie submerged beneath the lake. The 5-km-wide Volcano Island in north-central Lake Taal is the location of all historical eruptions. The island is composed of coalescing small stratovolcanoes, tuff rings, and scoria cones that have grown about 25% in area during historical time. Powerful pyroclastic flows and surges from historical eruptions have caused many fatalities.
Aira, Kyushu (Japan)
31.593°N, 130.657°E, Summit elev. 1117 m
JMA reported that during 20-27 January there were 27 explosions and nine non-explosive eruptive events detected by the Minamidake Crater (at Aira Caldera’s Sakurajima volcano) seismic network. Ash plumes rose as high as 2.2 km above the crater rim and material was ejected 1-1.7 km away from the crater. Crater incandescence was visible at night. The sulfur dioxide emission rate was very high at 4,400 tons/day on 20 January. 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.
Dukono, Halmahera (Indonesia)
1.693°N, 127.894°E, Summit elev. 1229 m
Based on satellite and wind model data, and information from PVMBG, the Darwin VAAC reported that during 22-28 January ash plumes from Dukono rose to 1.8-2.1 km (6,000-7,000 ft) a.s.l. and drifted in multiple directions. The Alert Level remained at 2 (on a scale of 1-4), and the public was warned to remain outside of the 2-km exclusion zone.
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.
Ebeko, Paramushir Island (Russia)
50.686°N, 156.014°E, Summit elev. 1103 m
Volcanologists in Severo-Kurilsk (Paramushir Island), about 7 km E of Ebeko, observed explosions during 19-20 January that sent ash plumes up to 3 km (10,000 ft) a.s.l.; ash plumes drifted E and caused ashfall in Severo-Kurilsk on 19 January. The Aviation Color Code remained at Orange (the second highest level on a four-color scale).
Geological summary: The flat-topped summit of the central cone of Ebeko volcano, one of the most active in the Kuril Islands, occupies the northern end of Paramushir Island. Three summit craters located along a SSW-NNE line form Ebeko volcano proper, at the northern end of a complex of five volcanic cones. Blocky lava flows extend west from Ebeko and SE from the neighboring Nezametnyi cone. The eastern part of the southern crater contains strong solfataras and a large boiling spring. The central crater is filled by a lake about 20 m deep whose shores are lined with steaming solfataras; the northern crater lies across a narrow, low barrier from the central crater and contains a small, cold crescentic lake. Historical activity, recorded since the late-18th century, has been restricted to small-to-moderate explosive eruptions from the summit craters. Intense fumarolic activity occurs in the summit craters, on the outer flanks of the cone, and in lateral explosion craters.
Etna, Sicily (Italy)
37.748°N, 14.999°E, Summit elev. 3295 m
INGV reported continuing eruptive activity at Etna’s Voragine Crater (VOR), New Southeast Crater (NSEC), and Northeast Crater (NEC) during 21-26 January. The cone in VOR produced Strombolian explosions which increased in frequency and resulted in rapid cone growth (especially the N part). Lava traveled down the S flank of the cone and into the adjacent Bocca Nuova Crater, filling the E crater (BN-2). Activity at NEC was characterized by discontinuous Strombolian activity and periodic emissions of very diffuse ash plumes. During 21-22 January there were several episodes of ash emissions at NSEC, originating from the vent that had opened on 11 December 2019 on the side of the saddle area. Ash emissions rarely rose form the E vent.
Geological summary: Mount Etna, towering above Catania, Sicily's second largest city, has one of the world's longest documented records of historical volcanism, dating back to 1500 BCE. Historical lava flows of basaltic composition cover much of the surface of this massive volcano, whose edifice is the highest and most voluminous in Italy. The Mongibello stratovolcano, truncated by several small calderas, was constructed during the late Pleistocene and Holocene over an older shield volcano. The most prominent morphological feature of Etna is the Valle del Bove, a 5 x 10 km horseshoe-shaped caldera open to the east. Two styles of eruptive activity typically occur, sometimes simultaneously. Persistent explosive eruptions, sometimes with minor lava emissions, take place from one or more summit craters. Flank vents, typically with higher effusion rates, are less frequently active and originate from fissures that open progressively downward from near the summit (usually accompanied by Strombolian eruptions at the upper end). Cinder cones are commonly constructed over the vents of lower-flank lava flows. Lava flows extend to the foot of the volcano on all sides and have reached the sea over a broad area on the SE flank.
Karangetang, Siau Island (Indonesia)
2.781°N, 125.407°E, Summit elev. 1797 m
PVMBG reported that during 20-26 January lava continued to effuse from Karangetang’s Main Crater (S), traveling as far as 1.8 km down the Nanitu, Pangi, and Sense drainages on the SW and W flanks. Sometimes dense white plumes rose 150 m above the summit. Incandescence from both summit craters was visible at night. The Alert Level remained at 2 (on a scale of 1-4).
Geological summary: Karangetang (Api Siau) volcano lies at the northern end of the island of Siau, about 125 km NNE of the NE-most point of Sulawesi island. The stratovolcano contains five summit craters along a N-S line. It 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 have produced pyroclastic flows.
1.697°S, 101.264°E, Summit elev. 3800 m
PVMBG reported that on 24 January a brown ash plume rose 500 m above Kerinci’s summit and drifted NW. The Alert Level remained at 2 (on a scale of 1-4), and the public was warned to remain outside of the 3-km exclusion zone.
Geological summary: Gunung Kerinci in central Sumatra forms Indonesia's highest volcano and is one of the most active in Sumatra. It is capped by an unvegetated young summit cone that was constructed NE of an older crater remnant. There is 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. The massive 13 x 25 km wide volcano towers 2400-3300 m above surrounding plains and is elongated in a N-S direction. Frequently active, Kerinci has been the source of numerous moderate explosive eruptions since its first recorded eruption in 1838.
Klyuchevskoy, Central Kamchatka (Russia)
56.056°N, 160.642°E, Summit elev. 4754 m
KVERT reported that a thermal anomaly over Klyuchevskoy was identified in satellite images during 17-24 January. Strombolian activity was visible daily, and Vulcanian activity was evident on 22 January. Explosions produced ash plumes that rose 5-6 km (16,400-19,700 ft) a.s.l.; an ash plume drifted 460 km E on 22 January. The Aviation Color Code remained at 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.
27.247°N, 140.874°E, Summit elev. 25 m
Based on satellite images, the Tokyo VAAC reported that during 25-26 January ash plumes from Nishinoshima rose 1.5 km (5,000 ft) a.s.l. and drifted SW, W, and NW.
Geological summary: The small island of Nishinoshima was enlarged when several new islands coalesced during an eruption in 1973-74. Another eruption that began offshore in 2013 completely covered the previous exposed surface and enlarged the island again. Water discoloration has been observed on several occasions since. The 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.
Sangeang Api, Indonesia
8.2°S, 119.07°E, Summit elev. 1912 m
The Darwin VAAC reported that on 23 January an ash emission from Sangeang Api rose to an altitude of 3 km (10,000 ft) a.s.l. and drifted NNE. The Alert Level remained at 2 (on a scale of 1-4).
Geological summary: Sangeang Api volcano, one of the most active in the Lesser Sunda Islands, forms a small 13-km-wide island off the NE coast of Sumbawa Island. Two large trachybasaltic-to-tranchyandesitic volcanic cones, Doro Api and Doro Mantoi, were constructed in the center and on the eastern rim, respectively, of an older, largely obscured caldera. Flank vents occur on the south side of Doro Mantoi and near the northern coast. Intermittent historical eruptions have been recorded since 1512, most of them during in the 20th century.
Semeru, Eastern Java (Indonesia)
8.108°S, 112.922°E, Summit elev. 3657 m
PVMBG reported that an eruption at Semeru continued during 20-26 January, producing ash plumes that rose as high as 500 m above the crater rim and drifted in multiple directions. The Alert Level remained at 2 (on a scale from 1-4); the public was warned to stay 1 km away from the active crater and 4 km away on the SSE flank.
Geological summary: Semeru, the highest volcano on Java, and one of its most active, lies at the southern end of a volcanic massif extending north to the Tengger caldera. The steep-sided volcano, also referred to as Mahameru (Great Mountain), rises above coastal plains to the south. Gunung Semeru was constructed south of the overlapping Ajek-ajek and Jambangan calderas. A line of lake-filled maars was constructed along a N-S trend cutting through the summit, and cinder cones and lava domes occupy the eastern and NE flanks. Summit topography is complicated by the shifting of craters from NW to SE. Frequent 19th and 20th century eruptions were dominated by small-to-moderate explosions from the summit crater, with occasional lava flows and larger explosive eruptions accompanied by pyroclastic flows that have reached the lower flanks of the volcano.
Sheveluch, Central Kamchatka (Russia)
56.653°N, 161.36°E, Summit elev. 3283 m
KVERT reported that a thermal anomaly over Sheveluch was identified in satellite images during 17-24 January. The Aviation Color Code remained at Orange (the second highest level on a four-color scale).
Geological summary: The high, isolated massif of Sheveluch volcano (also spelled Shiveluch) rises above the lowlands NNE of the Kliuchevskaya volcano group. The 1300 km3 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 seismic activity at Shishaldin remained above background levels during 22-28 January. Elevated surface temperatures continued to be identified in satellite images, though became weak during 26-28 January. Infrasound data suggested that minor explosions were occurring at the summit during 22-23 January. Small steam plumes from the summit were visible on 22, 23, and 26 January. The Aviation Color Code remained at Orange and the Volcano Alert Level remained at Watch.
Geological summary: The beautifully symmetrical Shishaldin is the highest and one of the most active volcanoes of the Aleutian Islands. The 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 steam plume often rises from its small summit crater. Constructed atop an older glacially dissected volcano, it is largely basaltic in composition. Remnants of an older ancestral volcano are exposed on the W 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.
Suwanosejima, Ryukyu Islands (Japan)
29.638°N, 129.714°E, Summit elev. 796 m
JMA reported that white plumes rose as high as 700 m above the rim of Suwanosejima’s Ontake Crater during 17-24 January. Crater incandescence was visible nightly. No changes in crater morphology were observed during an overflight on 21 January compared to 21 February 2019 observations; white plumes rose 400 m above the rim. The Alert Level remained at 2 (on a 5-level scale).
Geological summary: The 8-km-long, spindle-shaped island of Suwanosejima in the northern Ryukyu Islands consists of an andesitic stratovolcano with two historically active summit craters. The summit of the volcano is truncated by a large breached crater extending to the sea on the east flank that was formed by edifice collapse. Suwanosejima, one of Japan's most frequently active volcanoes, was in a state of intermittent strombolian activity from Otake, the NE summit crater, that began in 1949 and lasted until 1996, after which periods of inactivity lengthened. The largest historical eruption took place in 1813-14, when thick scoria deposits blanketed residential areas, and the SW crater produced two lava flows that reached the western coast. At the end of the eruption the summit of Otake collapsed forming a large debris avalanche and creating the horseshoe-shaped Sakuchi caldera, which extends to the eastern coast. The island remained uninhabited for about 70 years after the 1813-1814 eruption. Lava flows reached the eastern coast of the island in 1884. Only about 50 people live on the island.
39.42°S, 71.93°W, Summit elev. 2847 m
SERNAGEOMIN reported low levels of activity at Villarrica during 1-15 January, characterized by whitish gas plumes rising 250 m above the crater rim and nighttime crater incandescence observed during periods of clear weather. Sulfur dioxide gas emissions averaged around 349 tons per day, peaking at 468 tons per day on 3 January. Low-energy thermal anomalies were identified on 11, 13, and 14 January. POVI reported that lava fountaining from 4-5-m-diameter vents was visible during 18-20 and 22 January. Low levels of activity and minor explosions were noted on 27 January. SERNAGEOMIN maintained the Alert Level at Yellow, the second lowest level on a four-color scale. ONEMI maintained an Alert Level Yellow (the middle level on a three-color scale) for the municipalities of Villarrica, Pucón (16 km N), Curarrehue, and the commune of Panguipulli, and changed the exclusion zone for the public to a radius of 500 m around the crater.
Geological 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 the flanks. Plinian eruptions and pyroclastic flows that have extended up to 20 km from the volcano were 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 km2 of the volcano, and lahars have damaged towns on its flanks.