The Weekly Volcanic Activity Report: June 14 - 20, 2023

New activity/unrest was reported for 5 volcanoes from June 14 – 20, 2023. During the same period, ongoing activity was reported for 17 volcanoes.

New activity/unrest: Kilauea, Hawaiian Islands (USA) | Lokon-Empung, Sulawesi | Mayon, Luzon (Philippines) | Rincon de la Vieja, Costa Rica | Ubinas, Peru.

New activity/unrest

Kilauea, Hawaiian Islands (USA)

19.421°N, 155.287°W | Summit elev. 1222 m

HVO reported that the eruption on the floor of Kilauea’s Halema’uma’u Crater continued during 14-20 June. Activity was characterized by effusion primarily from the vent on the SW wall of the crater, circulation within the crater lakes, slow rise of the crater floor, eruptive tremor, and elevated sulfur dioxide levels (4,500-6,300 tonnes per day). Lava flows from vents at the base and top of a cone on the SW wall of Halema’uma’u entered the lava lake in the far SW portion of the crater; intermittent spattering from the cone was visible at night. Other eruptive vents within the SW lava lake (previously dome fountains) had ceased by 13 June. The surface of the SW lava lake slowly rose about 0.5 m per day during 13-15 June. Additionally, lava circulation continued within the central basin. At 0800 on 15 June the top of the SW wall cone collapsed, leading to nearly constant spattering from the top vent and a change in activity from the base vent. The central basin level has been dropping relative to the rising crater floor (due to lava accumulation underneath), allowing several flows from the SW lava lake to cascade into the basin.

By 16 June, renewed activity on the SW wall was producing vigorous fountaining to at least 10 m high with some higher spatters, with lava flowing into the SW lake. This activity continued into 19 June as the crater floor continued to rise, circulation in central basin slowed, and flows from the base of the SW wall cone changed paths. Around 1600 on 19 June activity rapidly declined, shown by a drop in the SW lake surface, decreased seismicity, and a transition to inflationary tilt from the deflationary trend of the previous two days. Seismic activity remained low and on 20 June HVO reported that the eruption had paused.

Geological summary: Kilauea overlaps the E flank of the massive Mauna Loa shield volcano in the island of Hawaii. Eruptions are prominent in Polynesian legends; written documentation since 1820 records frequent summit and flank lava flow eruptions interspersed with periods of long-term lava lake activity at Halemaumau crater in the summit caldera until 1924. The 3 x 5 km caldera was formed in several stages about 1,500 years ago and during the 18th century; eruptions have also originated from the lengthy East and Southwest rift zones, which extend to the ocean in both directions. About 90% of the surface of the basaltic shield volcano is formed of lava flows less than about 1,100 years old; 70% of the surface is younger than 600 years. The long-term eruption from the East rift zone between 1983 and 2018 produced lava flows covering more than 100 km2, destroyed hundreds of houses, and added new coastline.

Lokon-Empung, Sulawesi

1.358°N, 124.792°E | Summit elev. 1580 m

In a press release PVMBG reported increased emissions at Lokon-Empung on 13 June with dense white plumes rising 400 m above the rim of Tompaluan Crater and drifting S; a total of 12 earthquakes indicating emissions were recorded by the seismic network. The emissions were followed by a period of continuous tremor during 1835-2100. White steam-and-gas emissions of variable densities rose as high as 500 m and drifted N, W, and S during 14-20 June. During 2023 white emissions generally rose 20-150 m above the crater rim and seismicity was generally dominated by 1-2 daily shallow volcanic earthquakes. The volcano Alert Level remained at 2 (on a scale of 1-4) and the public was reminded not to approach the crater within a radius of 1.5 km.

Geological summary: The Lokong-Empung volcanic complex, rising above the plain of Tondano in North Sulawesi, includes four peaks and an active crater. Lokon, the highest peak, has a flat craterless top. The morphologically younger Empung cone 2 km NE has a 400-m-wide, 150-m-deep crater that erupted last in the 18th century. A ridge extending 3 km WNW from Lokon includes the Tatawiran and Tetempangan peaks. All eruptions since 1829 have originated from Tompaluan, a 150 x 250 m crater in the saddle between Lokon and Empung. These eruptions have primarily produced small-to-moderate ash plumes that sometimes damaged croplands and houses, but lava-dome growth and pyroclastic flows have also occurred.

Mayon, Luzon (Philippines)

13.257°N, 123.685°E | Summit elev. 2462 m

PHIVOLCS reported that lava-dome extrusion at Mayon’s summit crater continued during 14-20 June, generating frequent lava flows and pyroclastic density currents (PDCs, or pyroclastic flows), and additional evacuations. Sulfur dioxide emissions ranged from 149-193 tonnes per day (t/d) during 13-14 June, rising to 826-1,004 t/d during 15-18 June (above normal baseline values of 500 t/d), and then dropping to 389 t/d on 19 June. The total number of rockfalls ranged from 265-309 events per day, resulting from partial collapses of the growing lava dome and lava flows. PDCs were recorded during 13-14 June (7), 14-15 June (3), 15-16 June (13), 16-17 June (9), 17-18 June (11), 18-19 June (5), and 19-20 June (2); each event lasted 2-6 minutes based on seismic signals. Lava flows remained active, with debris collapses throughout the week sending material into the Mi-Isi (S) and Bonga (SE) drainages. By 20 June lava flows reached 2.5 km down the Mi-Isi and 1.8 km down the Bonga drainages, and debris flows extended 3.3 km from the crater. Ashfall during 15-16 June was reported in the communities of Buga (36 km W), Nabonton (9 km W), Ligao (16 km W), Purok 7 (12 km S), and San Francisco (11 km SW). The Disaster Response Operations Monitoring and Information Center (DROMIC) reported that by 20 June there had been 38,975 people affected, 20,139 displaced, and 18,749 taking shelter in 28 evacuation centers across Albay. The Alert Level remained at 3 (on a 0-5 scale), and residents were reminded to stay away from the 6-km-radius Permanent Danger Zone (PDZ).

Geological summary: Symmetrical Mayon, which rises above the Albay Gulf NW of Legazpi City, is the most active volcano of the Philippines. The steep upper slopes are capped by a small summit crater. Recorded eruptions since 1616 CE range from Strombolian to basaltic Plinian, with cyclical activity beginning with basaltic eruptions, followed by longer term andesitic lava flows. Eruptions occur predominately from the central conduit and have also produced lava flows that travel far down the flanks. Pyroclastic flows and mudflows have commonly swept down many of the approximately 40 ravines that radiate from the summit and have often damaged populated lowland areas. A violent eruption in 1814 killed more than 1,200 people and devastated several towns.

Rincon de la Vieja, Costa Rica

10.83°N, 85.324°W | Summit elev. 1916 m

OVSICORI-UNA reported that small phreatic explosions continued at Rincón de la Vieja during 14-19 June and gas-and-steam emissions were sometimes continuous. There were 1-3 daily events during 14-16 and 18 June; most were not observed due to darkness. A small event at 1804 on 18 June produced a steam-and-gas plume that rose 2 km above the crater rim.

Geological summary: Rincón de la Vieja, the largest volcano in NW Costa Rica, is a remote volcanic complex in the Guanacaste Range. The volcano consists of an elongated, arcuate NW-SE-trending ridge constructed within the 15-km-wide early Pleistocene Guachipelín caldera, whose rim is exposed on the south side. Sometimes known as the “Colossus of Guanacaste,” it has an estimated volume of 130 km3 and contains at least nine major eruptive centers. Activity has migrated to the SE, where the youngest-looking craters are located. The twin cone of Santa María volcano, the highest peak of the complex, is located at the eastern end of a smaller, 5-km-wide caldera and has a 500-m-wide crater. A Plinian eruption producing the 0.25 km3 Río Blanca tephra about 3,500 years ago was the last major magmatic eruption. All subsequent eruptions, including numerous historical eruptions possibly dating back to the 16th century, have been from the prominent active crater containing a 500-m-wide acid lake located ENE of Von Seebach crater.

Ubinas, Peru

16.355°S, 70.903°W | Summit elev. 5672 m

Instituto Geofísico del Perú (IGP) reported that seismicity at Ubinas had been increasing since mid-May, and that during 1-18 June fumarolic plumes rose 500 m above the crater rim. The Gobierno Regional de Moquegua raised the Alert Level to Yellow (the second lowest level on a four-color scale) on 20 June based on the recommendation from IGP.

Geological summary: A small, 1.4-km-wide caldera cuts the top of Ubinas, Perú’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. 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 3,700 years ago extend 10 km from the volcano. Widespread Plinian pumice-fall deposits include one of Holocene age about 1,000 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.

Ongoing activity

Ahyi, Mariana Islands (USA)

20.42°N, 145.03°E | Summit elev. -75 m

Unrest at Ahyi Seamount possibly continued during 13-20 June. A few small hydroacoustic signals coming from the direction of the seamount were detected by pressure sensors on Wake Island (2,270 km E) during 16-17 June. No surface activity was visible in satellite images. The Aviation Color Code remained at Yellow (the second lowest level on a four-color scale) and the Volcano Alert Level remained at Advisory (the second lowest level on a four-level scale).

Geological summary: Ahyi seamount is a large conical submarine volcano that rises to within 75 m of the sea surface about 18 km SE of the island of Farallon de Pajaros (Uracas) in the northern Marianas. Water discoloration has been observed there, and in 1979 the crew of a fishing boat felt shocks over the summit area of the seamount, followed by upwelling of sulfur-bearing water. On 24-25 April 2001 an explosive eruption was detected seismically by a station on Rangiroa Atoll, Tuamotu Archipelago. The event was well constrained (+/- 15 km) at a location near the southern base of Ahyi. An eruption in April-May 2014 was detected by NOAA divers, hydroacoustic sensors, and seismic stations.

Aira, Kyushu (Japan)

31.593°N, 130.657°E | Summit elev. 1117 m

JMA reported ongoing activity at both Minamidake Crater and Showa Crater (Aira Caldera’s Sakurajima volcano) during 13-19 June. Ash plumes from Showa were recorded at 1412 on 16 June that rose 1.3 km above the rim and drifted S, with another at 0710 on 17 June that rose up to 1 km and drifted E. Crater incandescence was observed at Minamidake crater during the night of 18 June. The Alert Level remained at 3 (on a 5-level scale), and the public was warned to stay 2 km away from both craters.

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.

Cotopaxi, Ecuador

0.677°S, 78.436°W | Summit elev. 5911 m

IG reported that moderate eruptive activity continued at Cotopaxi during 13-20 June. Small gas-and-steam emissions rose as high as 200 m above the crater rim and drifted W and SW during 13-14 and 17 June. Several gas emissions with minor ash content rose 100 m on 15 June, and several seismic signals possibly indicating similar emissions were detected on 16 June. Gas-and-ash plumes rose 500-700 m on 18 June. Gas-and-steam plumes with minor ash content rose 100-700 m and drifted W and SW during 19-20 June. Servicio Nacional de Gestión de Riesgos y Emergencias (SNGRE) maintained the Alert Level at Yellow (the second lowest level on a four-color scale).

Geological summary: The symmetrical, glacier-covered, Cotopaxi stratovolcano is Ecuador’s most well-known volcano and one of its most active. The steep-sided cone is capped by nested summit craters, the largest of which is about 550 x 800 m in diameter. Deep valleys scoured by lahars radiate from the summit of the andesitic volcano, and large andesitic lava flows extend to its base. The modern edifice has been constructed since a major collapse sometime prior to about 5,000 years ago. Pyroclastic flows (often confused in historical accounts with lava flows) have accompanied many explosive eruptions, and lahars have frequently devastated adjacent valleys. Strong eruptions took place in 1744, 1768, and 1877. Pyroclastic flows descended all sides of the volcano in 1877, and lahars traveled more than 100 km into the Pacific Ocean and western Amazon basin. Smaller eruptions have been frequent since that time.

Ebeko, Paramushir Island (Russia)

50.686°N, 156.014°E | Summit elev. 1103 m

KVERT reported that moderate activity at Ebeko was ongoing during 8-15 June. A thermal anomaly was identified in satellite images throughout the week. According to volcanologists in Severo-Kurilsk (Paramushir Island, about 7 km E), explosions during 8-9 and 11-13 June generated ash plumes that rose as high as 4 km (11,500 ft) a.s.l. and drifted both NE and SE. The Aviation Color Code remained at Orange (the second highest level on a four-color scale). Dates are based on UTC times; specific events are in local time where noted.

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.

Fuego, South-Central Guatemala

14.473°N, 90.88°W | Summit elev. 3763 m

INSIVUMEH reported that 1-6 explosions per hour were recorded at Fuego during 14-20 June, generating daily ash plumes that rose as high as 1.1 km above the crater rim. The explosions were often accompanied by avalanches, shock waves, and minor rumbling sounds. The ash plumes drifted 10-30 km W and SW, causing daily ashfall in areas downwind including Morelia (9 km SW), Panimaché I and II (8 km SW), Santa Sofía (12 km SW), Ceylon, El Porvenir (8 km ENE), Sangre de Cristo (8 km WSW), Yepocapa (8 km NW), La Rochela, San Andrés Osuna, and Finca Palo Verde.

Geological summary: Volcán Fuego, one of Central America’s most active volcanoes, is also one of three large stratovolcanoes overlooking Guatemala’s former capital, Antigua. The scarp of an older edifice, Meseta, lies between Fuego and Acatenango to the north. 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 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.

Great Sitkin, Andreanof Islands (USA)

52.076°N, 176.13°W | Summit elev. 1740 m

AVO reported that slow lava effusion continued at Great Sitkin during 14-20 June. The thick lava flow remained confined to the summit crater, and several small earthquakes were recorded daily. Elevated surface temperatures were observed during periods of clear satellite views during 16-17 June; weather clouds obscured webcam and satellite views on the other days. The Volcano Alert Level remained at Watch (the second highest level on a four-level scale) and the Aviation Color Code remained at Orange (the second highest level on a four-color scale).

Geological summary: The Great Sitkin volcano forms much of the northern side of Great Sitkin Island. A younger parasitic volcano capped by a small, 0.8 x 1.2 km ice-filled summit caldera was constructed within a large late-Pleistocene or early Holocene scarp formed by massive edifice failure that truncated an ancestral volcano and produced a submarine debris avalanche. Deposits from this and an older debris avalanche from a source to the south cover a broad area of the ocean floor north of the volcano. The summit lies along the eastern rim of the younger collapse scarp. Deposits from an earlier caldera-forming eruption of unknown age cover the flanks of the island to a depth up to 6 m. The small younger caldera was partially filled by lava domes emplaced in 1945 and 1974, and five small older flank lava domes, two of which lie on the coastline, were constructed along northwest- and NNW-trending lines. Hot springs, mud pots, and fumaroles occur near the head of Big Fox Creek, south of the volcano. Historical eruptions have been recorded since the late-19th century.

Karangetang, Sangihe Islands

2.781°N, 125.407°E | Summit elev. 1797 m

PVMBG reported that dense white gas-and-steam plumes from Karangetang were visible rising as high as 75 m and drifting in multiple directions during 14-20 June. Weather clouds obscured views at times on 14, 16, and 18 June. Webcam images published in the reports showed incandescence at Main Crater (S crater) and from material on the flanks of Main Crater at 0007 on 17 June and 0440 on 18 June. The Alert Level remained at 3 (on a scale of 1-4) and the public were advised to stay 2.5 km away from Main Crater with an extension to 3.5 km on the S and SE flanks.

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. 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 (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.

Krakatau, Sunda Strait

6.102°S, 105.423°E | Summit elev. 155 m

PVMBG reported that daily white gas-and-steam plumes rose as high as 200 m above Krakatau’s summit during 14-20 June. At 0822 on 19 June a dense white-to-gray ash plume rose 1.5 km and drifted SE. The Alert Level remained at 3 (on a scale of 1-4), and the public was warned to stay at least 5 km away 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 edifice, perhaps in 416 or 535 CE, formed a 7-km-wide caldera. Remnants of that 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 caused more than 36,000 fatalities, most as a result of 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.

Lewotolok, Lembata Island

8.274°S, 123.508°E | Summit elev. 1431 m

PVMBG reported that the eruption at Lewotolok continued during 14-20 June. White-and-gray ash plumes rose as high as 400 m above the summit and drifted W and NW during 15 and 17-18 June; white steam-and-gas emissions were visible on the other days. Strombolian explosions at the summit crater were visible in webcam images at 2242 on 14 June, 2137 on 17 June, and 2213 on 18 June. 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 summit crater in all directions.

Geological summary: The Lewotolok (or Lewotolo) stratovolcano occupies the eastern end of an elongated peninsula extending north into the Flores Sea, connected to Lembata (formerly Lomblen) Island by a narrow isthmus. It is symmetrical when viewed from the north and east. A small cone with a 130-m-wide crater constructed at the SE side of a larger crater forms the volcano’s high point. Many lava flows have reached the coastline. Eruptions recorded since 1660 have consisted of explosive activity from the summit crater.

Merapi, Central Java

7.54°S, 110.446°E | Summit elev. 2910 m

BPPTKG reported that the eruption at Merapi (on Java) continued during 9-15 June and seismicity remained at elevated levels. The SW lava dome produced 119 lava avalanches that traveled as far as 2 km down the SW flank (upstream in the Bebeng drainage). Morphological changes to the SW lava dome were due to continuing collapses of material. The Alert Level remained at 3 (on a scale of 1-4), and the public was warned to stay 3-7 km away from the summit based on location.

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 2,000 years ago, leaving a large arcuate scarp cutting the eroded older Batulawang volcano. Subsequent growth of the steep-sided Young Merapi edifice, its upper part unvegetated due to frequent 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.

Popocatepetl, Mexico

19.023°N, 98.622°W | Summit elev. 5393 m

CENAPRED reported that ongoing activity at Popocatépetl during 14-20 June included 39-180 daily steam-and-gas emissions, sometimes containing minor amounts of ash. According to the Washington VAAC, daily ash plumes rose to maximum altitudes of 5.8-6.7 km (19,000-22,000 ft) a.s.l., or up to 1.3 km above the summit, and drifted generally drifted S, SW, and W, causing ashfall in local communities. At 0337 on 17 June CENAPRED noted a moderate explosion that ejected ballistic material as far as 2.5 km from the crater. Minor ashfall was reported in Hueyapan (16 km SSW), Tetela del Volcán (18 km SW), Yecapixtla (29 km SW) and Ayala (47 km SW) in Morelos, as well as Amecameca (18 km NW) and Atlautla (16 km W) in the State of Mexico during 14-15 June. Minor ashfall during 15-16 June was reported in Amecameca, Ayapango (21 km NW), Chalco (37 km NW), Ecatzingo (15 km SW), Temamatla (30 km NW), Tepetlixpa (20 km W), Tlalmanalco (26 km NW) and Tenango del Aire (28 km NW) in the State of Mexico. Reports of minor ashfall came from Ixtapaluca (42 km NW), Valle de Chalco (44 km NW), La Paz (50 km NW), Nezahualcóyotl (56 km NW), Amecameca, Atlautla, Ayapango, Cocotitlan (34 km NW), Chalco, Ecatzingo, Temamatla, Tenango del Aire, Tepetlixpa and Tlalmanalco in the State of Mexico during 16-17 June. Minor ashfall during 18-19 June was again reported in Tepoztlan (49 km W), Cuernavaca (63 km WSW), Ocuituco (24 km SW), Cuautla (43 km SW), Atlatlahucan (30 km SW), Jiutepec (59 km SW) and Emiliano Zapata (62 km SW), Morelos; Ixtapaluca, La Paz, Valle de Chalco, Nezahualcóyotl (54 km NW), Chicoloapan (48 km NW), Atlautla, Ecatzingo, Tonatico in the State of Mexico. Seismicity included periods of low-to-moderate amplitude, high-frequency tremor for 274-567 minutes each day, three volcano-tectonic earthquakes of M 1.2-1.5 were recorded during 15-16 June, and 19 minutes of low-amplitude, harmonic tremor during 16-17 June. The Alert Level remained at Yellow, Phase Two (the middle level on a three-color scale) and the public was warned to stay 12 km away from the crater.

Geological summary: Volcán Popocatépetl, whose name is the Aztec word for smoking mountain, rises 70 km SE of Mexico City to form North America’s 2nd-highest volcano. The glacier-clad stratovolcano contains a steep-walled, 400 x 600 m wide crater. The generally symmetrical volcano is modified by the sharp-peaked Ventorrillo on the NW, a remnant of an earlier volcano. At least three previous major cones were destroyed by gravitational failure during the Pleistocene, producing massive debris-avalanche deposits covering broad areas to the south. The modern volcano was constructed south of the late-Pleistocene to Holocene El Fraile cone. Three major Plinian eruptions, the most recent of which took place about 800 CE, have occurred since the mid-Holocene, accompanied by pyroclastic flows and voluminous lahars that swept basins below the volcano. Frequent historical eruptions, first recorded in Aztec codices, have occurred since Pre-Columbian time.

Sabancaya, Peru

15.787°S, 71.857°W | Summit elev. 5960 m

Instituto Geofísico del Perú (IGP) reported moderate levels of activity at Sabancaya during 12-18 June with a daily average of 18 explosions. Gas-and-ash plumes rose as high as 1.5 km above the summit and drifted SE, E, and NE. Five thermal anomalies originating from the lava dome in the summit crater were identified in satellite data. Minor inflation continued to be detected near Hualca Hualca (4 km N). The Alert Level remained at Orange (the second highest level on a four-color scale) and the public were warned to stay outside of 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.

Sangay, Ecuador

2.005°S, 78.341°W | Summit elev. 5286 m

IG reported a high level of activity at Sangay during 13-20 June and the seismic network recorded 327-2,190 daily explosions. Gas, steam, and ash plumes were occasionally observed in IG webcam images or described in Washington VAAC volcanic activity notifications, though weather clouds sometimes prevented observations. Ash-and-gas plumes rose as high as 1.8 km above the summit and drifted W during 13-15 June. Gas-and-steam plumes rose less than 1 km during 16-17 June. Ash plumes rose as high as 1.2 km and drifted W on 18 June. Incandescence at the summit was visible in webcam images. Overnight during 18-19 June the lava flow on the SE flank was incandescent and pyroclastic material descended the SE flank as far as 500 m several times. During 19-20 June several ash-and-gas emissions rose as high as 550 m above the summit and drifted SW. Incandescence at the summit was visible multiple times. Minor ashfall was reported in Llagos parish, Chunchi (73 km SW) on 20 June. Servicio Nacional de Gestión de Riesgos y Emergencias (SNGRE) maintained the Alert Level at Yellow (the second lowest level on a four-color scale).

Geological summary: The isolated Sangay volcano, located east of the Andean crest, is the southernmost of Ecuador’s volcanoes and its most active. The steep-sided, glacier-covered, dominantly andesitic volcano grew within the open calderas of two previous edifices which were destroyed by collapse to the east, producing large debris avalanches that reached the Amazonian lowlands. The modern edifice dates back to at least 14,000 years ago. It towers above the tropical jungle on the east side; on the other sides flat plains of ash have been eroded by heavy rains into steep-walled canyons up to 600 m deep. The earliest report of an eruption was in 1628. Almost continuous eruptions were reported from 1728 until 1916, and again from 1934 to the present. The almost constant activity has caused frequent changes to the morphology of the summit crater complex.

Semeru, Eastern Java

8.108°S, 112.922°E | Summit elev. 3657 m

PVMBG reported that the eruption at Semeru continued during 14-20 June. White-and-gray ash plumes rose 100-700 m and drifted N, NW, W, and S during 16 and 18-20 June; emissions were not observed on the other days. The Alert Level remained at 3 (third highest on a scale of 1-4). The public was warned to stay at least 5 km away from the summit in all directions, 13 km from the summit to the SE, 500 m from the banks of the Kobokan drainage as far as 17 km from the summit, and to avoid other drainages including the Bang, Kembar, and Sat, due to lahar, avalanche, and pyroclastic flow hazards.

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.

Stromboli, Aeolian Islands (Italy)

38.789°N, 15.213°E | Summit elev. 924 m

INGV reported ongoing activity at Stromboli during 12-18 June. The Strombolian activity was centered at two vents in Area N (one each at craters N1 and N2), within the upper part of the Sciara del Fuoco, and from four vents in Area C-S (South-Central Crater) in the crater terrace. Low- and medium-intensity explosions at a rate of 3-7 per hour from Area N2 ejected mainly coarse material (bombs and lapilli), sometimes mixed with ash, up to 150 m above the vents. Sporadic explosive activity at N1 ejected mainly ash mixed with smaller amounts of coarse material. Low- to high-intensity explosions averaged 8-14 per hour from the three vents in sector S2 (Area C-S), ejecting a mix of coarse material and ash; weak spattering was sometimes observed. Weak emission of gas sometimes accompanied explosive events.

Geological summary: Spectacular incandescent nighttime explosions at Stromboli have long attracted visitors to the “Lighthouse of the Mediterranean” in the NE Aeolian Islands. This volcano 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 took place between about 13,000 and 5,000 years ago. The active summit vents are located at the head of the Sciara del Fuoco, a prominent scarp that formed about 5,000 years ago due to a series of slope failures which extends 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.

Suwanosejima, Ryukyu Islands (Japan)

29.638°N, 129.714°E | Summit elev. 796 m

JMA reported that the eruption at Suwanosejima’s Ontake Crater continued during 14-19 June. A total of 526 volcanic earthquakes, 26 explosions, and 18 eruptive events were recorded by seismic monitoring stations throughout the week; activity was most notable during 15-16 June with totals of 164 volcanic earthquakes and 10 explosions. Ash plumes were observed daily; the tallest plumes rose 2 km above the crater rim on 15 and 16 June. Continuous emissions during 0936-1355 on 16 June rose as high as 2 km and drifted SE and SW. Some events ejected large volcanic blocks up to 400 m from the crater during 14-18 June. Incandescent ejecta from explosions during the nights of 18-19 June were sometimes visible in webcam images. Occasional ashfall and rumbling noises were reported in Toshima village (3.5 km SSW). The Alert Level remained at 2 (on a 5-level scale) and the public was warned to stay at least 2 km away from the crater.

Geological summary: The 8-km-long island of Suwanosejima in the northern Ryukyu Islands consists of an andesitic stratovolcano with two historically active summit craters. The summit is truncated by a large breached crater extending to the sea on the east flank that was formed by edifice collapse. One of Japan’s most frequently active volcanoes, it was in a state of intermittent Strombolian activity from Otake, the NE summit crater, between 1949 and 1996, after which periods of inactivity lengthened. The largest recorded 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 open 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.

Taal, Luzon (Philippines)

14.002°N, 120.993°E | Summit elev. 311 m

PHIVOLCS reported continuing low-level unrest at Taal during 13-20 June characterized by elevated seismicity, upwelling in the lake, and sulfur dioxide gas emissions. There were 20-38 daily volcanic earthquakes recorded during 13-17 June and a total of 11 recorded during 19-20 June. There were 2-46 daily periods of tremor, each lasting 2-67 minutes long. Daily white steam-and-gas plumes (sometimes voluminous) rose as high as 3 km above the lake and drifted NE, NW, and SW; voggy conditions were reported during 16-17 June. Upwelling gasses and hot fluids in the lake were visible during 14-17 June. Sulfur dioxide emissions averaged 7,643 and 2,177 tonnes per day on 15 June and 19 June, respectively. The Alert Level remained at 1 (on a scale of 0-5), and PHIVOLCS reminded the public that the entire Taal Volcano Island was a Permanent Danger Zone (PDZ).

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 observed eruptions. The island is composed of coalescing small stratovolcanoes, tuff rings, and scoria cones. Powerful pyroclastic flows and surges have caused many fatalities.

References:

Smithsonian Institution / US Geological Survey – Weekly Volcanic Activity Report – June 14 – 20, 2023 – Managing Editor: Sally Sennert. Written by Zachary W. Hastings.

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