Blog note: And great earthquakes shall be in diverse places, and famines, and pestilences; and fearful sights and great signs shall there be from heaven. (Luke 21:11). Jesus is giving a series of prophecies about what to look for as the age of grace comes to a close. This verse from Luke is one of many such prophecies from throughout the Bible. 2017 was the worst year in recorded history for the intensity, frequency, severity, duration and occurrence of a large number of severe natural disasters worldwide. Earthquakes, volcanoes, hurricanes, typhoons, cyclones, torrential flooding, unprecedented wildfires in unusual places, devastating droughts, excessive/scorching heat setting records everywhere, record snowfalls in Europe and Russia. Snow in the Arabia. This list can go on. Most studied eschatologists believe these ‘fearful sights’ and massive natural disasters are all part of the ‘CONVERGENCE’ of signs that this Biblical and prophetic age is closing. Most people who study prophecy are familiar with the routine reference(s) made that these things will be like a woman having labor pains that occur in greater severity, frequency, size and duration prior to giving birth. End of note.
The Weekly Volcanic Activity Report: October 17 – 23, 2018
Posted by TW on October 25, 2018. Watchers.news
New activity/unrest was reported for 3 volcanoes between October 17 and 23, 2018. During the same period, ongoing activity was reported for 15 volcanoes.
New activity/unrest: Kerinci, Indonesia | Kuchinoerabujima, Ryukyu Islands (Japan) | Sarychev Peak, Matua Island (Russia).
Ongoing activity: Aira, Kyushu (Japan) | Dukono, Halmahera (Indonesia) | Ebeko, Paramushir Island (Russia) | Etna, Sicily (Italy) | Fuego, Guatemala | Ibu, Halmahera (Indonesia) | Kadovar, Papua New Guinea | Krakatau, Indonesia | Merapi, Central Java (Indonesia) | Piton de la Fournaise, Reunion Island (France) | Sabancaya, Peru | Santa Maria, Guatemala | Sheveluch, Central Kamchatka (Russia) | Turrialba, Costa Rica | Veniaminof, United States.
The Weekly Volcanic Activity Report is a cooperative project between the Smithsonian’s Global Volcanism Program and the US Geological Survey’s Volcano Hazards Program. Updated by 23:00 UTC every Wednesday, notices of volcanic activity posted are preliminary and subject to change as events are studied in more detail. This is not a comprehensive list of all of Earth’s volcanoes erupting during the week. Carefully reviewed, detailed reports on various volcanoes are published monthly in the Bulletin of the Global Volcanism Network.
1.697°S, 101.264°E, Elevation 3800 m
Based on satellite images, ground observers, and wind model data, the Darwin VAAC reported that during 18-22 October ash plumes from Kerinci rose to an altitude of 4.3 km (14,000 ft) a.s.l. and drifted N, W, WSW, and SW.
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. This volcano is located within the Tropical Rainforest Heritage of Sumatra, a UNESCO World Heritage property.
Kuchinoerabujima, Ryukyu Islands (Japan)
30.443°N, 130.217°E, Elevation 657 m
JMA reported that a very small eruption at Kuchinoerabujima’s Shindake Crater was recorded at 1831 on 21 October, with additional activity between 2110 on 21 October and 1350 on 22 October. Plumes rose 200 m above the crater rim. During an overflight on 22 October observers noted ash in the emissions, though no morphological changes to the crater nor ash deposits were seen. The Alert Level remained at 3 (on a scale of 1-5).
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 west 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 Shintake, formed after the NW side of Furutake was breached by an explosion. All historical eruptions have occurred from Shintake, although a lava flow from the S flank of Furutake that reached the coast has a very fresh morphology. Frequent explosive eruptions have taken place from Shintake 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.
Sarychev Peak, Matua Island (Russia)
48.092°N, 153.2°E, Elevation 1496 m
KVERT reported that a thermal anomaly over Sarychev Peak was visible in satellite images on 15 October. Weather clouds obscured views on the other days during 12-19 October. The Aviation Color Code remained at Orange.
Geological summary: Sarychev Peak, one of the most active volcanoes of the Kuril Islands, occupies the NW end of Matua Island in the central Kuriles. The andesitic central cone was constructed within a 3-3.5-km-wide caldera, whose rim is exposed only on the SW side. A dramatic 250-m-wide, very steep-walled crater with a jagged rim caps the volcano. The substantially higher SE rim forms the 1496 m high point of the island. Fresh-looking lava flows, prior to activity in 2009, had descended in all directions, often forming capes along the coast. Much of the lower-angle outer flanks of the volcano are overlain by pyroclastic-flow deposits. Eruptions have been recorded since the 1760s and include both quiet lava effusion and violent explosions. Large eruptions in 1946 and 2009 produced pyroclastic flows that reached the sea.
Aira, Kyushu (Japan)
31.593°N, 130.657°E, Elevation 1117 m
JMA reported that occasional, very small events occurred at Minamidake crater (at Aira Caldera’s Sakurajima volcano) during 12-19 October. Sulfur dioxide emissions were slightly less than 400 tons per day on 17 October. 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, Elevation 1229 m
Based on satellite data, wind model data, and notices from PVMBG, the Darwin VAAC reported that during 18-23 October ash plumes from Dukono rose to altitudes of 1.5-2.1 km (5,000-7,000 ft) a.s.l. and drifted E and NE.
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, Elevation 1103 m
Volcanologists in Severo-Kurilsk (Paramushir Island), about 7 km E of Ebeko, observed explosions during 12-19 October that sent ash plumes to 4.5 km (14,800 ft) a.s.l. Ash plumes drifted in multiple directions, and caused ashfall in Severo-Kurilsk during 14-16 October. 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, Elevation 3295 m
INGV reported that during 15-21 October activity at Etna was characterized by gas emissions at the summit craters, with periodic Strombolian activity from vents in Bocca Nuova, Northeast Crater (NEC), Southeast Crater (SEC), and New Southeast Crater (NSEC). Strombolian activity at the N vent in the W part of Bocca Nuova’s (BN-1) crater floor ejected incandescent material higher that the crater rim. Spattering from the southernmost vent was also visible. Gas emissions increased at Voragine Crater from a vent that formed on 7 August 2016 on the E rim of the crater, and the crater continued to gradually widen and deepen. NEC activity was characterized by gas emissions and explosive activity of variable frequency and intensity. Fumarolic plumes rose from the rim and crater walls of NSEC and SEC. The E vent in NSEC produced Strombolian explosions and ash emissions which rapidly dispersed.
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. This volcano is located within the Mount Etna, a UNESCO World Heritage property.
14.473°N, 90.88°W, Elevation 3763 m
INSIVUMEH and CONRED reported that on 20 October hot lahars descended Fuego’s Las Lajas (SE) and Mineral drainages, carrying blocks up to 2 m in diameter along with branches and tree trunks. The lahars were 20-30 m wide and 2 m deep. During 20-23 October there were 8-15 weak explosions recorded per hour, producing gray ash plumes that rose 750-850 m above the crater rim and drifted 12 km W and SW. Ashfall was reported in areas downwind, including Morelia (9 km SW), Santa Sofia (12 km SW), Sangre de Cristo (8 km WSW), Finca Palo Verde, Panimaché (8 km SW), and San Pedro Yepocapa (8 km NW). Lavafountains rose 100-200 m high. Avalanches of blocks descended the El Jute (SE), Ceniza (SSW), and Las Lajas (SE) drainages, with material reaching vegetated areas.
Geological 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.
Ibu, Halmahera (Indonesia)
1.488°N, 127.63°E, Elevation 1325 m
PVMBG reported that at 1223 on 19 October an event at Ibu generated an ash plume that rose 400 m above the crater rim and drifted E. Another event at 1809 on 22 October generated an ash plume that rose 400 m above the crater rim and drifted N. On both days seismic signals indicated explosions and rock avalanches. The Alert Level remained at 2 (on a scale of 1-4), and the public was warned to stay at least 2 km away from the active crater, and 3.5 km away on the N side.
Geological summary: The truncated summit of Gunung Ibu stratovolcano along the NW coast of Halmahera Island has large nested summit craters. The inner crater, 1 km wide and 400 m deep, contained several small crater lakes through much of historical time. The outer crater, 1.2 km wide, is breached on the north side, creating a steep-walled valley. A large parasitic cone is located ENE of the summit. A smaller one to the WSW has fed a lava flow down the W flank. A group of maars is located below the N and W flanks. Only a few eruptions have been recorded in historical time, the first a small explosive eruption from the summit crater in 1911. An eruption producing a lava dome that eventually covered much of the floor of the inner summit crater began in December 1998.
Kadovar, Papua New Guinea
3.608°S, 144.588°E, Elevation 365 m
According to the Darwin VAAC, ash plumes from Kadovar were visible in satellite images on 21 October drifting NE at an altitude of 2.4 km (8,000 ft) a.s.l.
Geological summary: The 2-km-wide island of Kadovar is the emergent summit of a Bismarck Sea stratovolcano of Holocene age. Kadovar is part of the Schouten Islands, and lies off the coast of New Guinea, about 25 km N of the mouth of the Sepik River. The village of Gewai is perched on the crater rim. A 365-m-high lava dome forming the high point of the andesitic volcano fills an arcuate landslide scarp that is open to the south, and submarine debris-avalanche deposits occur in that direction. Thick lava flows with columnar jointing forms low cliffs along the coast. The youthful island lacks fringing or offshore reefs. No certain historical eruptions are known; the latest activity was a period of heightened thermal phenomena in 1976.
6.102°S, 105.423°E, Elevation 813 m
Based on satellite data, the Darwin VAAC reported that during 17-19 October ash plumes from Anak Krakatau rose to altitudes of 1.5-2.4 km (5,000-8,000 ft) a.s.l.and drifted in multiple directions. The Alert Level remained at 2 (on a scale of 1-4); residents and visitors were warned not to approach the volcano within 2 km of the crater.
Geological summary: The renowned volcano Krakatau (frequently misstated as Krakatoa) lies in the Sunda Strait between Java and Sumatra. Collapse of the ancestral Krakatau edifice, perhaps in 416 CE, formed a 7-km-wide caldera. Remnants of this ancestral volcano are preserved in Verlaten and Lang Islands; subsequently Rakata, Danan and Perbuwatan volcanoes were formed, coalescing to create the pre-1883 Krakatau Island. Caldera collapse during the catastrophic 1883 eruption destroyed Danan and Perbuwatan volcanoes, and left only a remnant of Rakata volcano. This eruption, the 2nd largest in Indonesia during historical time, caused more than 36,000 fatalities, most as a result of devastating tsunamis that swept the adjacent coastlines of Sumatra and Java. Pyroclastic surges traveled 40 km across the Sunda Strait and reached the Sumatra coast. After a quiescence of less than a half century, the post-collapse cone of Anak Krakatau (Child of Krakatau) was constructed within the 1883 caldera at a point between the former cones of Danan and Perbuwatan. Anak Krakatau has been the site of frequent eruptions since 1927. This volcano is located within the Ujung Kulon National Park, a UNESCO World Heritage property.
Merapi, Central Java (Indonesia)
7.54°S, 110.446°E, Elevation 2910 m
PVMBG reported that during 12-18 October the lava dome in Merapi’s summit crater grew at a rate of 6,200 cubic meters per day, faster than the previous week. By 18 October the volume of the dome, based on photos from the SE sector, was an estimated 201,000 cubic meters. White emissions of variable density rose a maximum of 100 m above the summit. The Alert Level remained at 2 (on a scale of 1-4), and residents were warned to remain outside of the 3-km exclusion zone.
Geological summary: Merapi, one of Indonesia’s most active volcanoes, lies in one of the world’s most densely populated areas and dominates the landscape immediately north of the major city of Yogyakarta. It is the youngest and southernmost of a volcanic chain extending NNW to Ungaran volcano. Growth of Old Merapi during the Pleistocene ended with major edifice collapse perhaps about 2000 years ago, leaving a large arcuate scarp cutting the eroded older Batulawang volcano. Subsequently growth of the steep-sided Young Merapi edifice, its upper part unvegetated due to frequent eruptive activity, began SW of the earlier collapse scarp. Pyroclastic flows and lahars accompanying growth and collapse of the steep-sided active summit lava dome have devastated cultivated lands on the western-to-southern flanks and caused many fatalities during historical time.
Piton de la Fournaise, Reunion Island (France)
21.244°S, 55.708°E, Elevation 2632 m
OVPF reported that the eruption at Piton de la Fournaise continued during 17-23 October. Strong gas emissions rose from the main vent as well as from areas along the lava tube. Periodic field surveys indicated active lava flows, several tens of meters long, at the base of the cone, and possibly active lava in the main vent.
Geological summary: The massive Piton de la Fournaise basaltic shield volcano on the French island of Réunion in the western Indian Ocean is one of the world’s most active volcanoes. Much of its more than 530,000-year history overlapped with eruptions of the deeply dissected Piton des Neiges shield volcano to the NW. Three calderas formed at about 250,000, 65,000, and less than 5000 years ago by progressive eastward slumping of the volcano. Numerous pyroclastic cones dot the floor of the calderas and their outer flanks. Most historical eruptions have originated from the summit and flanks of Dolomieu, a 400-m-high lava shield that has grown within the youngest caldera, which is 8 km wide and breached to below sea level on the eastern side. More than 150 eruptions, most of which have produced fluid basaltic lava flows, have occurred since the 17th century. Only six eruptions, in 1708, 1774, 1776, 1800, 1977, and 1986, have originated from fissures on the outer flanks of the caldera. The Piton de la Fournaise Volcano Observatory, one of several operated by the Institut de Physique du Globe de Paris, monitors this very active volcano. This volcano is located within the Pitons, Cirques et Remparts de I’ile de la Reunion, a UNESCO World Heritage property.
15.787°S, 71.857°W, Elevation 5960 m
Observatorio Vulcanológico del Sur del IGP (OVS-IGP) and Observatorio Vulcanológico del INGEMMET (OVI) reported that explosions at Sabancaya averaged 23 per day during 15-21 October. Hybrid earthquakes were infrequent and of low magnitude. Gas-and-ash plumes rose as high as 3 km above the crater rim and drifted 40 km W, NE, and SE. The MIROVA system detected five thermal anomalies, and on 19 October the sulfur dioxide gas flux was high at 2,200 tons per day. The report noted that the public should not approach the crater within a 12-km radius.
Geological summary: Sabancaya, located in the saddle NE of Ampato and SE of Hualca Hualca volcanoes, is the youngest of these volcanic centers and the only one to have erupted in historical time. The oldest of the three, Nevado Hualca Hualca, is of probable late-Pliocene to early Pleistocene age. The name Sabancaya (meaning “tongue of fire” in the Quechua language) first appeared in records in 1595 CE, suggesting activity prior to that date. Holocene activity has consisted of Plinian eruptions followed by emission of voluminous andesitic and dacitic lava flows, which form an extensive apron around the volcano on all sides but the south. Records of historical eruptions date back to 1750.
Santa Maria, Guatemala
14.757°N, 91.552°W, Elevation 3745 m
INSIVUMEH reported that during 20-23 October explosions at Santa María’s Santiaguito lava-dome complex generated ash plumes that rose 500-700 m and drifted SW and W. Avalanches of material descended the W and E flanks of the lava dome.
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.
Sheveluch, Central Kamchatka (Russia)
56.653°N, 161.36°E, Elevation 3283 m
KVERT reported that a weak thermal anomaly over Sheveluch was identified in satellite data during 14-15 October; weather clouds prevented views on the other days during 12-19 October. 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.
Turrialba, Costa Rica
10.025°N, 83.767°W, Elevation 3340 m
OVSICORI-UNA reported frequent Strombolian events at Turrialba since 5 October. Periodic gas-and-ash emissions rose 200-500 m above the crater rim and drifted E, NW, and SW during 17-23 October.
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 edifice covers an area of 500 km2. 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.
Veniaminof, United States
56.17°N, 159.38°W, Elevation 2507 m
AVO reported that the eruption at Veniaminof continued during 10-16 October, as evidenced by elevated surface temperatures from lava fountains and flows visible in satellite and webcam data, and low-level continuous tremor. Satellite data indicated that the W part of the S-flank flow field was active. A persistent steam plume, visible in webcam views, also contained sulfur dioxide and possible ash. The plume was particularly robust on 18 October, drifting 30 km NE; plumes drifted NE on 19 October and S the next morning. The Aviation Color Code remained at Orange and the Volcano Alert Level remained at Watch.
Geological summary: Massive Veniaminof volcano, one of the highest and largest volcanoes on the Alaska Peninsula, is truncated by a steep-walled, 8 x 11 km, glacier-filled caldera that formed around 3700 years ago. The caldera rim is up to 520 m high on the north, is deeply notched on the west by Cone Glacier, and is covered by an ice sheet on the south. Post-caldera vents are located along a NW-SE zone bisecting the caldera that extends 55 km from near the Bering Sea coast, across the caldera, and down the Pacific flank. Historical eruptions probably all originated from the westernmost and most prominent of two intra-caldera cones, which rises about 300 m above the surrounding icefield. The other cone is larger, and has a summit crater or caldera that may reach 2.5 km in diameter, but is more subdued and barely rises above the glacier surface.