quote:Mayor eruption Bezymianny
A major explosive eruption took place at Russia's Bezymianny volcano at 04:53 UTC on Friday, June 16, 2017. By 05:10 UTC, ash plume from the eruption reached an altitude of 12.2 km (40 000 feet) above sea level and a distance of 40 km (25 miles) NE of the volcano, according to the Tokyo VAAC. This is the strongest eruption of this volcano since September 2012.
At 05:43 UTC, KVERT said they raised the Aviation Color Code from Orange to Red. "Ash cloud as big as 28 x 25 km (17.4 x 15.5 miles) drifts to the northeast of the volcano," the Observatory said, adding that ash explosions up to 10 - 15 km (32 800 - 49 200 feet) a.s.l. could occur at any time. "Ongoing activity could affect international and low-flying aircraft.
This is the strongest eruption of Bezymianny volcano since September 1/2, 2012. It comes just two days after a powerful eruption of nearby Sheveluch volcano ejected ash to an altitude 12 km (39 360 feet) a.s.l. Sheveluch is located 90 km (56 miles) NE of Bezymianny.
The last significant eruption of Bezymianny volcano, although nowhere near today's, took place on March 9, 2017. Based on webcam observations, an ash plume rose to altitudes of 6 - 7 km (20 000 - 23 000 feet) a.s.l. and drifted 20 km (12.4 miles) northeast. The Aviation Color Code was raised from Yellow to Orange. About 30 minutes later, an ash plume rose to altitudes of 7 - 8 km (23 000 - 26 200 feet) a.s.l. and drifted 60 km (37 miles) northwest. Later that day a 274-km-long (170 miles) ash plume identified in satellite images drifted NW at altitudes of 4 - 4.5 km (13 100 - 14 800 feet) a.s.l.; the majority of the leading part of the plume contained a significant amount of ash. A lava flow traveled down the NW part of the lava dome.
Bezymianny is one the most active volcanoes in the world. In 1955, for the first time in history, it started to erupt, and after six months it produced a catastrophic eruption with the total volume of eruptive products over 3 km3.
The lava dome began to grow in the explosive caldera immediately after the catastrophe and still continues. At least 44 Vulcanian-type strong explosive eruptions of Bezymianny occurred between 1965 - 2012.
quote:Increased seismic activity at underwater Lō‘ihi volcano, Hawaii
Since the end of February 2017, the Hawaii Volcano Observatory (HVO) seismic analysts have noted a slight uptick in the number of earthquakes near underwater Lō‘ihi volcano. The quakes appear to be clustered roughly 10 to 12 km (6 - 7 miles) below sea level and extend from beneath the summit region of Lō‘ihi to the south. The most recent confirmed eruption of this volcano occurred in 1996.
From January 2015 through February 2017, there was, on average, one located Lō‘ihi earthquake per month. Since then, the rate of earthquakes has gradually increased. As of June 22 (the last HVO update on this matter), there have been 51 located earthquakes in the Lō‘ihi region.
"Without permanent seismic stations at Lō‘ihi, because the highest point of the volcano is 1 km (0.62 miles) underwater, it is not possible to locate earthquakes there as accurately as we can at Kīlauea or Mauna Loa," HVO said. "However, we can state that the June 2017 earthquakes appear to be clustered roughly 10 - 12 km (6 - 7 miles) below sea level and extend from beneath the summit region of Lō‘ihi to the south."
Interestingly, the roughly 170 earthquakes located in the area of Lō‘ihi between 2010 and 2016 occurred away from the summit region. They were primarily beneath the northern flanks of Lō‘ihi, and extended to significantly greater depths below the volcano. The significance of this difference is unclear, HVO says.
As early as 1952, HVO scientists interpreted occasional earthquake swarms in the Lō‘ihi region as reflecting active volcanism there. In fact, the earthquakes were key to recognizing that the seamount is actually an active volcano.
Earthquake activity alone does not conclusively indicate that Lō‘ihi is erupting. But the locations of recent earthquakes directly beneath the volcano's summit region plausibly suggest magmatic or volcanic origin, such as adjustments within the magma reservoir or volcanic edifice. "We would, however, expect to see many more earthquakes associated with an eruption," the observatory notes.
The most recent confirmed eruption of Lō‘ihi occurred in 1996. That year, an energetic earthquake swarm began in July and quickly intensified, motivating a scientific expedition to Lō‘ihi to seize an unprecedented opportunity to possibly observe a submarine eruption. Thousands of earthquakes, including over a dozen with magnitudes greater than 4.5, were recorded from beneath the summit and south flank of the volcano between July and September 1996.
Subsequent viewing and mapping of the Lō‘ihi summit region showed that, consistent with magma movement from beneath the summit area, a significant portion of it had collapsed. Fresh pillow lavas and glassy fragments collected during submersible dives also confirmed the occurrence of an eruption.
"Because Lō‘ihi is still so deep beneath the ocean's surface, the USGS regards Lō‘ihi as a low- to very low-threat volcano. Thus, there are no immediate plans for additional monitoring instruments and our views of Lō‘ihi for the foreseeable future will be strictly seismological," the observatory concluded.