Sunday, March 27, 2016

GLOBAL VOLCANISM: The Latest Report Of Volcanic Eruptions, Activity, Unrest And Awakenings – March 12-26, 2016! [PHOTOS]

Nyiragongo's intra-crater lava flows last week, cascading into the main lava lake (Image: João Cunha Monteiro / Facebook)

March 27, 2016 - EARTH - The following constitutes the new activity, unrest and ongoing reports of volcanoes across the globe.

Nyiragongo (DRCongo): The mainly effusive activity from the new secondary vent inside the volcano's caldera continues with little changes.

Lava cascading into the central lava lake of Nyiragongo volcano (Image: Jason Sehorn)

By now, new lava flows have surrounded the central pit (containing the main lava lake), covered most of the lower platform and cascade into the central vent at multiple locations.

Suwanose-jima (Ryukyu Islands): The strombolian activity continues at the Otake crater continues. In the past days, it has been more intense, generating bright glow visible from neighboring islands and ash plumes that rose up to approx. 1 km.

Eruption at Suwanose-jima.

Sinabung (Sumatra, Indonesia): Activity of the volcano continues essentially unchanged with very slow lava extrusion and intermittent small to moderate explosions at the lava dome.

These occur at irregular intervals almost daily, generating ash plumes that rise 1-3 km: last evening, an explosion produced a plume that rose approx. 2500 m, local observers reported. This morning, an ash plume to 9,000 ft (2.7 km) altitude was reported by Darwin VAAC.

Copahue (Chile/Argentina): Ash emissions from the volcano (which had been less vigorous and more intermittent over the previous days) have increased this morning and become continuous. Buenos Aires VAAC reported a plume at approx. 12,000 ft (3.6 km) altitude extending 35 km east from the volcano.

Ash plume from Copahue

Alaid (Northern Kuriles): The new eruptive phase that started in late February continues. An intense thermal anomaly has been detected from the volcano's summit area on satellite imagery and weak ash emissions extending approx. 60 km NW from the island were observed yesterday and this morning (Tokyo VAAC).

Thermal radiation from Alaid volcano (MODIS / Mirova)

Akita-Komaga-take (Honshu): Elevated seismic activity has been detected by Japanese volcanologists.
No other parameters (visual fumarolic activity, deformation etc) seem to be above background levels and no particular alert was raised.

Colima (Western Mexico): Mild explosive activity continues from the volcano. Mostly small explosions occur at irregular intervals of typically several hours from the summit vent where a small new lava dome is present and probably growing slowly.

Colima eruption.

An aerial photograph from February 29 shows the dome with a diameter of approx. 40-50 meters.

Telica (Nicaragua): After a period of several days of calm, lava glow has again become visible over night from the crater; during the day, increased degassing can be noted.

Lava glow from Telica's crater

Likely, the new fissure that formed on March 2, has again become active and erupted a small (if not tiny) amount of lava into the crater.

Soputan (North Sulawesi, Indonesia): A small group of VolcanoDiscovery just returned from a visit to Soputan. While clouds prevented detailed observations most of the time, glow was visible from the summit at night and moderate steaming during the day.

Glow from Soputan. (Photo: Ingrid / VolcanoDiscovery)

No other unusual events were observed (rockfalls, movements of the recent lava flows etc).

This suggests that effusive activity if at all is very weak at the lava dome occupying the summit crater.

Momotombo (Nicaragua): Explosions seem to have ceased during the past week. Glow remains visible at the crater, suggesting that lava continues to be present there.

Momotombo volcano's glow

Etna (Sicily, Italy):
INGV Catania published the result of very high-resolution satellite-based measurements of ground deformation of Etna during the period between February 2015 - February 2016.

They show that Etna's dominant trend of deformation has changed from inflation (in blue) to deflation since the latest eruption in early December.

Deformation at Etna in late Dec 2015 (INGV)

Inflation of the entire volcanic edifice continued until November 2015, before the violent paroxysmal episodes occurred in December. During this event, the deflation that accompanied the eruptive activity has almost completely neutralized the preceding inflation, which likely means that most of the accumulated magma inside the volcano had been erupted during the recent activity.

This also suggests that Etna, currently very calm, might not be in for significant eruptions in the near future of the coming months (although only she herself knows for sure...)

The data were obtained using a modern interferometric techniques from TOPSAR (Terrain Observation with Progressive Scans SAR) radar images acquired by the Sentinel-1A satellite and have a precision in the sub-centimeter range.

Other interesting observations include eastward sliding movements of the northeastern and eastern flanks of Etna during and after the latest eruptive phase.

Mt. Etna - Monitoraggio delle deformazioni del suolo con Sentinel 1 A. (INGV Catania)

Sakurajima (Kyushu, Japan): The activity at the volcano has decreased again over the past 2 weeks. The average size and frequency of explosions has dropped to one every few days (compared to several / day earlier in February). So far, March has only seen 3 explosions recorded by JMA.

Something new, however, is that a number of the recent explosions came not from the Showa crater, but from the Minamidake summit crater, the older one of the two, located west above the former one.

Eruption from Sakurajima's Minamidake crater

Minamidake had been Sakurajima's main active vent for decades since 1955, until a new crater on its eastern flank began to form and gradually "take over" in 2006 and became known as the Showa crater. In the past few years, only very few explosions were recorded from Minamidake,- nearly all activity had been at Showa crater, but this might have changed very recently.

From Smithsonian / USGS Weekly Volcanic Activity Report March 2-8, 2016:
During February 29  to March 4, JMA reported that two explosions from Showa Crater at Aira Caldera’s Sakurajima volcano ejected tephra as far as 500 m. At 0038 on March 4, an explosion at Minamidake summit crater generated an ash plume that rose 1.6 km. The Alert Level remained at 3 (on a 5-level scale). 

Shishaldin (Aleutian Islands, Alaska): The alert level was lowered back to normal status. Detectable activity (visible observations and satellite-based data) has been decreasing steadily of the past several months, the Alaska Volcano Observatory reported:

"There has been a steady decrease in detected thermal activity at Shishaldin over the past several months. No anomalous activity has been observed in several clear satellite images of Shishaldin since moderately elevated surface temperatures were detected on January 13. Airwaves associated with low-level explosive degassing have not been detected in infrasound data since February 7.

Low-amplitude seismic tremor consistent with an open, degassing system continues to be seen in seismic data and is considered to be within the bounds of background activity for Shishaldin. AVO is therefore downgrading the status of Shishaldin Volcano from aviation color code YELLOW to GREEN and from volcano alert level ADVISORY to NORMAL."

Rincón de la Vieja (Costa Rica): The volcano had a new explosion from its crater lake last Wednesday March 8. The eruption threw deposits of mud and ash onto the northern side of the crater to up to 120 m distance from the rim and generated a small plume of ash that caused light ash fall in nearby villages in up to 6 km distance to the north.

The activity at the volcano had started to increase already in 2015. Volcanologists have found evidence of several similar explosions that occurred in the past months, but the most recent one on Wednesday seems to have been significantly larger (although still small in itself).

Eruption at Rincón de la Vieja volcano (OVSICORI-UNA)

The new ash deposit on the northern crater flank (OVSICORI-UNA)

Close-up of the erupted ash: b) and c) show glassy lava from fresh magma (OVSICORI-UNA)

The most interesting news, however, comes from the analysis of the ejected ash. OVSICORI-UNA staff found that besides fragmented older rocks and sulfur, about 3-10 % of the ejected ash particles are glassy shards from juvenile (i.e. new) magma.

This means that the explosions were not entirely driven by steam only (so-called phreatic explosions), but involved a component of fresh magma that seems to have recently risen to shallow depths near the surface and was contributing to the energy of the explosion (phreatomagmatic activity). This could (but not necessarily must) signify that more eruptive activity, potentially stronger, is going to occur at the volcano in the near to medium-term future.

- Volcano Discovery.

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