Etna volcano updates and eruption news:
Etna volcano update: Regular "mini-eruptions" at SE crater - an interpretation
Friday May 19, 2017 08:48 AM | BY: T
Strombolian activity at the SE crater's saddle vent and the peaks of tremor accompanying each short-lived episode (image: Boris Behncke / INGV Catania)Since 11 May, Etna has been in an unusual state of activity. At remarkably regular intervals of approx. 8 hours, the "saddle vent", located between Etna's old and new Southeast Crater, has been producing more than 20 brief episodes of mild strombolian activity, each accompanied by a short-lived increase in volcanic tremor amplitude. The episodes are further characterized by the absence of strong degassing.
What causes this unusual and certainly transient behavior is not exactly known. Researcher Dr Marco Neri tries to give an explanation in an article on La Gazzetta Siracusana(loosely translated):
"In fact, Etna volcano produces "mini-eruptions" that last a few tens of minutes, located at the top of the New South-East Crater, at about 3300 meters. There would be nothing strange about this, except that these events occur with an impressive regularity, about 3 a day, and at fairly constant intervals of about eight hours. A phenomenon that closely resembles that of geysers, although in this case it is magma to erupt at the surface and not water. ...
These small eruptive events are always accompanied by an increase in the amplitude of volcanic tremor, which corresponds to a vibration produced by movements of volcanic fluids circulating within the eruptive duct. When the magma approaches the surface and erupts, tremor increases sharply. ... Therefore, the tremor graph shows a series of almost regular peaks for amplitude and intervals. It's like volcano's hiccups!
"Why do these mini-eruptions happen? What makes them so regular and frequent? Without claiming to always understand everything about a volcano, especially Etna which is full of surprises, we can try to give an answer:
Etna's feeding system, and in particular the eruptive ducts that feeds these eruptions, can be imagined like a narrow and long pressure pot. The heat of the magma is similar to the fire lit under the pot, while the gases separating from the magma and accumulating in the top of the duct correspond to the water vapor that forms inside the pot when the water is heated and bubbles.
Finally, the eruptive vent from which the mini-eruptions occur can be compared to the valve of our pressure cooker. Every time the gas pressure inside the duct exceeds a certain critical value, the "valve" opens and some magma erupts on the surface. And to complete the similitude, the characteristic "whistle" of the pot valve that opens can be compared to the hissing sounds that people nearby perceive during these mini-eruptions.
"The extraordinary nature of the phenomenon that we observe at the moment lies, however, in the fact of the remarkable regularity of the mini-eruptions, showing that the system has reached an excellent balance between the magma that is being fed from below into the upper ducts and the magma that is lost (expelled) from the system during these mini-eruptions.
What will happen?
How can the hiccups of Etna cease? The phenomenon may last for a long time, at least until this balance between the rising magma and the eruptions stays in place. Things will eventually change when the available magma volume will decrease, or, if the volume of fresh magma rising from below increases significantly, leading probably to eruptive episodes such as observed during the past months.
Also the geometry of the upper portion of the the vent, or, to stay in the image, our "volcano" vent valve, plays an important role: should this vent change, e.g. collapse, or become obstructed, it would certainly also change the course followed by magma to reach the surface, as well as the energy needed to produce an eruption.
In this case, it would change the eruptive style of the volcano and perhaps also the position of the eruptive vent." (Marco Neri / INGV Catania)
Thursday, Apr 27, 2017
Etna volcano Volcanic Ash Advisory: STROMBOLIANS EXPLOSIONS OCCUR BUT NO SIGNIFICANT ASH EMISSION IS DETECTED
Wednesday, Apr 26, 2017
Wednesday, Apr 19, 2017
After a pause of 4 days, a new (mainly effusive) eruptive episode started this morning around 11:30 local time. Accompanied by mild strombolian activity from the summit vent of the SE crater cone, a new lava flow began to descend on the southern flank of the SE crater complex. ... [more]
Wednesday, Apr 19, 2017
Friday, Apr 14, 2017
After 48 hours of pause since the previous, short-lived eruptive episode, a new effusive eruptive phase began last evening, involving 3 vents. ... [more]