 |
| 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.
Source: 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.
