Stronger eruptions at two Alaska volc...

Stronger eruptions at two Alaska volcanoes

There are 2 comments on the KMIZ story from Jun 25, 2013, titled Stronger eruptions at two Alaska volcanoes. In it, KMIZ reports that:

Two Alaskan volcanoes that began minor eruptions weeks ago are showing their strongest seismic activity yet, emitting small amounts of lava and ash along with smoke plumes, the Alaska Volcano Observatory said Tuesday.

Join the discussion below, or Read more at KMIZ.

El ameen

Europe

#1 Jun 25, 2013
PEOPLE OF THE WORLD SHOULD NO THAT,ISAH A,S IMAMUL MAHDI JESUS THE MESSEIH IS PRESENT ON EARTH AND HE SAID MORE AND MORE CALAMITIES ARE AHAID OF THE WORLD TILL THE WHOLE WORLD NO THE REALITY OF GOD. ABDULLAHI BIN ABDULLAH ISAH ZAHIRAN.

“Geologist [I'm Climate Change]”

Since: Mar 07

formerly Nuneaton

#2 Jun 26, 2013
Just gave the prior poster another can of spam,(he must like the taste).

Volcanoes mentioned are fed by a long horizontal fracture running from approximately the volcano to the backarc following the rebound/long duration mercalli X earthquake (r/lx) & bloody great big tsunami of the 1780s or thereabouts that gave a bloody great big tsunami (~85m @ an Aleut village on Sanak).

Several other long series volcanoes (such as Shishaldin, and Augustine) appear to be fed by similar fractures created by either the 1st or 2nd r/lx of that year.

As the fractures are long and relatively thin the pressure in them is increased by convergence of the 2 plates (Beringia & Pacific), which is fastest in the W. and slowest E. The semi periodicity is because when the slug of magma travelling down the fissure is squirted into the volcano & erupts, there is a time gap for a new magma slug to form & migrate. Add to that the convergence @ the volcano part of the arc tightens the crust there so the fracture has to dilate the part adjacent to the volcano to enable it to inject into the magma chamber.

Long fracture fed volcanoes such as Sangay may erupt continuously for decades, but most as a result of tightening of the forearc & arc, have eruptions in series as a result of the squirt of little blobs. Nice to see the 2 in Alaska popping up on semi regular schedule.

Fun bit is that r/lx can produce a set of parallel fractures. When an overpressured parallel fracture breaks into the main the result is a big eruption from a fracture filled with primary magma that had been cooling & exsolving gas in situ for centuries (Boom). Handy therefore to keep watching that space as an occasional biggie may turn up (this has happened in the records of mayon volcano {Philippines}, which underwent r/lx in the early hispanic records.

I am still waiting for Shishaldin, it is a mite late.

Have a nice day: Ag

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