The Weekly Volcanic Activity Report: June 26 - July 2, 2019

The Weekly Volcanic Activity Report: June 26 - July 2, 2019

New activity/unrest was reported for 5 volcanoes from June 26 - July 2, 2019. During the same period, ongoing activity was reported for 11 volcanoes.

New activity/unrest: Manam, Papua New Guinea | Mauna Loa, Hawaiian Islands (USA) | Raikoke, Kuril Islands (Russia) | Ubinas, Peru | Ulawun, New Britain (Papua New Guinea).

Ongoing activity: Dukono, Halmahera (Indonesia) | Ebeko, Paramushir Island (Russia) | Klyuchevskoy, Central Kamchatka (Russia) | Krakatau, Indonesia | Sangeang Api, Indonesia | Santa Maria, Guatemala | Semeru, Eastern Java (Indonesia) | Sheveluch, Central Kamchatka (Russia) | Stromboli, Aeolian Islands (Italy) | White Island, North Island (New Zealand) | Yasur, Vanuatu.

New activity/unrest

Manam, Papua New Guinea

4.08°S, 145.037°E, Elevation 1807 m

RVO reported that RSAM values at Manam began increasing on 27 June and then spiked from 540 to over 1,400 within a short period of time (~30 min). According to news articles, residents reported hearing thundering noises around 0100 on 28 June. An eruption plume was visible in satellite images around 0620 drifting SW, around the time residents reported the start of the eruption. The Darwin VAAC issued a notice stating that by 0910 the ash plume had risen to 15.2 km (50,000 ft) a.s.l. and was drifting SW. Pyroclastic flows descended the W and NE flanks. About 3,775 people evacuated their homes. Additional ash plumes rose to 4.6 km (15,000 ft) a.s.l. and drifted W, and by 1700 the higher-altitude plume had detached from the volcano and continued to drift SW. A thermal anomaly persisted on 29 June, and the next day an ash plume rose to 2.4 km (8,000 ft) a.s.l. and drifted W.

Air Niugini stopped all aircraft overnighting in Madang due to the eruption. On 30 June they resumed operations at Hoskins airport, after rerouting all flights out of nearby airports during 29-30 June.

Geological 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.

Mauna Loa, Hawaiian Islands (USA)

19.475°N, 155.608°W, Elevation 4170 m

HVO reported that during the previous several months earthquake and ground deformation rates at Mauna Loa were elevated above background levels. During the first half of 2018 the seismic network recorded fewer than 20 shallow, small-magnitude earthquakes per week. Following a significant earthquake swarm in October, the rate increased to at least 50 events per week beneath the summit, upper Southwest Rift Zone, and upper west flank. These locations were similar to those that preceded eruptions in 1975 and 1984. GPS and satellite RADAR data detected deformation consistent with recharge of the shallow magma storage system. The increased seismicity and deformation indicated that Mauna Loa is no longer at background levels, prompting HVO to raise the Aviation Color Code to Yellow and the Volcano Alert Level to Advisory. HVO noted that an eruption was not imminent.

Geological summary: Massive Mauna Loa shield volcano rises almost 9 km above the sea floor to form the world's largest active volcano. Flank eruptions are predominately from the lengthy NE and SW rift zones, and the summit is cut by the Mokuaweoweo caldera, which sits within an older and larger 6 x 8 km caldera. Two of the youngest large debris avalanches documented in Hawaii traveled nearly 100 km from Mauna Loa; the second of the Alika avalanches was emplaced about 105,000 years ago (Moore et al. 1989). Almost 90% of the surface of the basaltic shield volcano is covered by lavas less than 4000 years old (Lockwood and Lipman, 1987). During a 750-year eruptive period beginning about 1500 years ago, a series of voluminous overflows from a summit lava lake covered about one fourth of the volcano's surface. The ensuing 750-year period, from shortly after the formation of Mokuaweoweo caldera until the present, saw an additional quarter of the volcano covered with lava flows predominately from summit and NW rift zone vents. This volcano is located within the Hawaiian Islands, a UNESCO World Heritage property.

Raikoke, Kuril Islands (Russia)

48.292°N, 153.25°E, Elevation 551 m

SVERT and KVERT reported that during 25 June-1 July steam-and-gas plumes with ash rose 1.5-2 km above Raikoke and drifted WNW based on satellite images. The Aviation Color Code was lowered to Yellow on 25 June and then to Green on 27 June.

Geological summary: A low truncated volcano forms the small barren Raikoke Island, which lies 16 km across the Golovnin Strait from Matua Island in the central Kuriles. The oval-shaped basaltic island is only 2 x 2.5 km wide and rises above a submarine terrace. The steep-walled crater, highest on the SE side, is 700 m wide and 200 m deep. Lava flows mantle the eastern side of the island. A catastrophic eruption in 1778, during which the upper third of the island was said to have been destroyed, prompted the first volcanological investigation in the Kuril Islands two years later. Reports of eruptions in 1777 and 1780 are erroneous (Gorshkov, 1970). Another powerful eruption in 1924 greatly deepened the crater and changed the outline of the island.

Ubinas, Peru

16.355°S, 70.903°W, Elevation 5672 m

Instituto Geofísico del Perú (IGP) and INGEMMET reported that seismic activity at Ubinas remained elevated during 24-30 June; volcano-tectonic events averaged 200 per day and signals indicating fluid movement averaged 38 events per day. Emissions of gas, water vapor, and ash rose from the crater and drifted N and NE based on webcam views and corroborated with satellite data. According to a news article an eruption plume rose 400 m above the crater rim and drifted 10 km NE. The Alert Level was raised to Yellow (on a 4-level scale) on 27 June.

Geological 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.

Ulawun, New Britain (Papua New Guinea)

5.05°S, 151.33°E, Elevation 2334 m

RVO reported that on 27 June diffuse white plumes rose from Ulawun’s summit crater and incandescence was visible from pyroclastic or lava flow deposits on the N flank from the significant eruption the day before. The seismic station located 11 km NW of the volcano recorded low RSAM values between 2 and 50. According to the Darwin VAAC a strong thermal anomaly was visible in satellite images, though not after 1200. Ash from 26 June explosions continued to move away from the volcano and became difficult to discern in satellite images by 1300, though a sulfur dioxide signal persisted; ash at 13.7 km (45,000 ft) a.s.l. drifted SW to SE and dissipated by 1620, and ash at 16.8 km (55,000 ft) a.s.l. drifted NW to NE and dissipated by 1857. RVO noted that at 1300 on 27 June satellite images captured an ash explosion not reported by ground-based observers likely due to cloudy weather conditions. The Alert Level was lowered to Stage 1.

RSAM values slightly increased at 0600 on 28 June and fluctuated between 80 to 150 units afterwards. During 28-29 June diffuse white plumes continued to rise from the crater and from the North Valley vent. On 29 June a news article stated that around 11,000 people remained evacuated to shelters.

Geological summary: The symmetrical basaltic-to-andesitic Ulawun stratovolcano is the highest volcano of the Bismarck arc, and one of Papua New Guinea's most frequently active. The volcano, also known as the Father, rises above the north coast of the island of New Britain across a low saddle NE of Bamus volcano, the South Son. The upper 1000 m is unvegetated. A prominent E-W escarpment on the south may be the result of large-scale slumping. Satellitic cones occupy the NW and E flanks. A steep-walled valley cuts the NW side, and a flank lava-flow complex lies to the south of this valley. Historical eruptions date back to the beginning of the 18th century. Twentieth-century eruptions were mildly explosive until 1967, but after 1970 several larger eruptions produced lava flows and basaltic pyroclastic flows, greatly modifying the summit crater.

Ongoing activity

Dukono, Halmahera (Indonesia)

1.693°N, 127.894°E, Elevation 1229 m

Based on satellite and wind model data, and notices from PVMBG, the Darwin VAAC reported that during 26 June-2 July ash plumes from Dukono rose to an altitude of 2.1 km (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, Elevation 1103 m

KVERT reported that a thermal anomaly over Ebeko was identified in satellite images on 23 June; weather clouds obscured views of the volcano on the other days during 21-28 June. 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.

Klyuchevskoy, Central Kamchatka (Russia)

56.056°N, 160.642°E, Elevation 4754 m

KVERT reported that a weak thermal anomaly over Klyuchevskoy was visible in satellite images on 23 and 26 June, and a gas-and-steam plume with some ash content drifted E on 26 June. The Aviation Color Code remained at Orange (the second highest level on a four-color scale).

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. This volcano is located within the Volcanoes of Kamchatka, a UNESCO World Heritage property.

Krakatau, Indonesia

6.102°S, 105.423°E, Elevation 813 m

PVMBG reported that Anak Krakatau’s seismic network recorded periods of increased activity with three eruptive events detected during 25-26 June, four events detected on 1 July, and one event on 2 July. The event was not followed by visible ash emissions, though observations were hindered by weather conditions. The Alert Level remained at 2 (on a scale of 1-4), and the public was warned to remain outside of the 2 km radius hazard zone from 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 or 535 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, and left only a remnant of Rakata. 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.

Sangeang Api, Indonesia

8.2°S, 119.07°E, Elevation 1949 m

The Darwin VAAC reported that on 27 June ash plumes from Sangeang Api rose to 2.1 km (7,000 ft) a.s.l. and drifted NW. A thermal anomaly was also visible. On 29 June a discrete ash puff that rose to 2.4 km (8,000 ft) a.s.l. drifted NW, and steam emissions were ongoing.

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, 1949-m-high Doro Api and 1795-m-high 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.

Santa Maria, Guatemala

14.757°N, 91.552°W, Elevation 3745 m

INSIVUMEH reported increased activity at Santa María's Santiaguito lava-dome complex in a special bulletin posted on 2 July. They note that during the previous two years activity was characterized as low, with 10-15 weak explosions per day, and emissions composed mainly of water vapor with minor ash content. Beginning on 28 June the seismic network recorded a gradual increase of the number and intensity of explosions, with 35-40 events per day. These explosions were weak-to-moderate intensity and produced ash plumes that rose 1-1.3 km above the complex and drifted S and SW. Ashfall was recorded in areas downwind including Patzulín, El Faro, Horizontes, Las Marías, Loma Linda, and San Marcos Palajunoj. Block avalanches descended the SE, S, and SW flanks and sometimes generated ash plumes.

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 stratovolcano has a sharp-topped, conical profile that is cut on the SW flank by a 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.

Semeru, Eastern Java (Indonesia)

8.108°S, 112.922°E, Elevation 3657 m

PVMBG reported that at 0830 on 26 June an eruption at Semeru produced an ash plume that rose around 600 m above the summit and drifted SW. 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. This volcano is located within the Bromo Tengger Semeru-Arjuno, a UNESCO Biosphere Reserve property.

Sheveluch, Central Kamchatka (Russia)

56.653°N, 161.36°E, Elevation 3283 m

KVERT reported that a thermal anomaly over Sheveluch’s lava dome was identified daily in satellite images during 21-28 June. Explosions on 24 and 27 June generated ash plumes that rose to 4.5 km (14,800 ft) a.s.l. and drifted E and SW, respectively. 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.

Stromboli, Aeolian Islands (Italy)

38.789°N, 15.213°E, Elevation 924 m

INGV reported that during 30 June-2 July activity at Stromboli was characterized by ongoing low-to-medium intensity Strombolian explosions and degassing from multiple vents within the crater terrace. A high-energy explosion from vent C in Area C-S (South Central crater area) was recorded at 2303 on 25 June. The event lasted for about 28 seconds, ejected material that fell onto most of the crater terrace and into the Valle della Luna, and widened the vent.

Geological summary: Spectacular incandescent nighttime explosions at this volcano have long attracted visitors to the "Lighthouse of the Mediterranean." Stromboli, the NE-most of the Aeolian Islands, has lent its name to the frequent mild explosive activity that has characterized its eruptions throughout much of historical time. The small island is the emergent summit of a volcano that grew in two main eruptive cycles, the last of which formed the western portion of the island. The Neostromboli eruptive period from about 13,000 to 5000 years ago was followed by formation of the modern edifice. The active summit vents are located at the head of the Sciara del Fuoco, a prominent horseshoe-shaped scarp formed about 5000 years ago as a result of the most recent of a series of slope failures that extend to below sea level. The modern volcano has been constructed within this scarp, which funnels pyroclastic ejecta and lava flows to the NW. Essentially continuous mild strombolian explosions, sometimes accompanied by lava flows, have been recorded for more than a millennium. This volcano is located within the Isole Eolie (Aeolian Islands), a UNESCO World Heritage property.

White Island, North Island (New Zealand)

37.52°S, 177.18°E, Elevation 321 m

GeoNet reported that earthquake swarms at White Island were recorded in May and beginning on 20 June. Even though both swarms were interpreted as fault activity and no unusual volcanic activity was observed, GeoNet increased monitoring of the volcano. Earthquake swarms can increase the likelihood of landslides.

A gas flight was conducted on 26 June because of the heightened monitoring and measurements were found to be 1,886 tons per day, three times the previous values measured in May. This was also the highest value recorded since 2013 and the second highest since regular measurements began in 2003. The Volcanic Alert Level was raised to 2 (on a scale of 0-5) and the Aviation Color Code was raised to Yellow. Two more gas flights found lower emissions values; sulfur dioxide flux was 880 tons per day on 28 June and 693 tons per day on 29 June. In addition, new measurements found no changes to fumarolic temperatures and modeling of ground deformation suggested the ongoing earthquake swarm was tectonic and did not reflect increased volcanic activity. The Volcanic Alert Level was lowered back to 1, with no change to the Aviation Color Code.

Geological summary: Uninhabited 2 x 2.4 km White Island, one of New Zealand's most active volcanoes, is the emergent summit of a 16 x 18 km submarine volcano in the Bay of Plenty about 50 km offshore of North Island. The island consists of two overlapping andesitic-to-dacitic stratovolcanoes; the summit crater appears to be breached to the SE, because the shoreline corresponds to the level of several notches in the SE crater wall. Volckner Rocks, four sea stacks that are remnants of a lava dome, lie 5 km NNE. Intermittent moderate phreatomagmatic and strombolian eruptions have occurred throughout the short historical period beginning in 1826, but its activity also forms a prominent part of Maori legends. Formation of many new vents during the 19th and 20th centuries has produced rapid changes in crater floor topography. Collapse of the crater wall in 1914 produced a debris avalanche that buried buildings and workers at a sulfur-mining project.

Yasur, Vanuatu

19.532°S, 169.447°E, Elevation 361 m

On 27 June the Vanuatu Meteorology and Geo-Hazards Department (VMGD) reported that recent observations and data from Yasur’s seismic network confirmed ongoing sometimes strong explosions. The Alert Level remained at 2 (on a scale of 0-4). VMGD reminded residents and tourists that hazardous areas were near and around the volcanic crater, within a 395-m-radius permanent exclusion zone, 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. The active cone 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.

Source: GVP

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