Volcano activity of August 1, 2012 - Etna, Cleveland, Yasur, Cumbal, Batu Tara and Sakurajima

This (almost) daily post intends to follow up the activity changes of volcanoes all over the world.
This post is written by geologist Richard Wilson who specializes in Volcano seismicity and Armand Vervaeck. Please feel free to tell us about new or changed activity if we haven't written about it. -

August 1, 2012 volcano activity

According to INGEOMINAS, the Observatorio de Pasto reported that during 25-31 July seismic signals at Cumbal volcano, Colombia related to movement of fluid decreased compared to the previous week; earthquake swarms were detected on 26, 27, 29, and 30 July. The number and magnitude of earthquakes generated by fracturing rock increased.

Following an assessment during 7-12 July, the Geohazards Observatory team concluded that explosive activity at Yasur volcano, Vanuatu had slightly increased, becoming stronger and more frequent, and shifting from Strombolian to sub-Plinian. Bombs ejected from the vents fell in the crater, around the summit area, and on the tourist walk and parking area. The explosions were heard, felt, and observed from nearby villages and schools. Activity at all three volcanic vents was characterized by degassing, ash emissions, and ejection of bombs. On 13 July the Alert Level was raised to 3 (on a scale of 0-4).

AVO reported that cloud cover mostly prevented satellite and web camera observations of Cleveland volcano, Alaska during 25-31 July. Slightly elevated surface temperatures were detected in satellite images during 25-26 and 29-30 July. The Volcano Alert Level remained at Watch and the Aviation Color Code remained at Orange.

Etna volcano, Sicily showed also some action last night. The Time-Lapse we have recorded from the Lave webcam shows consistent incandescent action. Volcanic seismicity remains higher than normal.
Update : seismicity decreased a lot during the evening hours. The action may be over for a while.

Activity observed by satellites
VAAC reports also Volcanic Ash clouds at the same volcanoes than the last couple of days : Batu Tara volcano, Indonesia (ash clouds up to 7000 ft or 2.1 km) and Sakurajima volcano Japan (ash clouds up to 7000 ft or 2.1 km). Sakurajima showed the latest explosion at 00:45 UTC
SO2 satellite images are showing strong emissions for both Popocatepetl volcano and Kilauea volcano.

Interesting articles
Pre-eruption Activity In Conduits Affect Volcanic Ejections
In addition to being fairly unpredictable, volcanoes can eject a wide range of material, from mile-high plums of black ash to a deadly hail of fist-sized pumice. These ejections travel extremely fast and can reach internal temperatures between 750 to 1,500 degrees Fahrenheit. The prevailing theory has been that the difference in particle size determined when bubbling magma deep below the volcano converts into a rising stream of gas and rock bits during a process known as fragmentation.However, a recent study published in Nature Geoscience indicates that the size of the ejected particles depends more on how often those particles collide as they race up the volcano’s conduits on their way to the surface. This means that the farther rock particles have to travel—the more likely they will be pulverized into a fine ash. Read more ...

Time-Lapse Video Etna activity July 31 -- August 1