This time we actually got to see it
all happening in its different phases. One is left with a truly vast
respect for the actual scale of what may happen with a volcano and an
understanding of how a volcano sequences through the different
chambers.
I suspect that we need to go check of a
lot of volcanoes to determine if a similar sequence is apparent in
thee assays. This will provide us a pile of new interpretive data.
It certainly makes Mt St Helen look like a tame volcano and also
shows us that any volcano has serious potential to hugely out perform
historical norms.
A string of chambers could sit sealed
for thousands of years while the closest to the surface erupt
regularly. Think Santorini as a scary example. You can be sure
frequent earlier eruptions made it all appear safe, just like all the
other so popular volcanoes we know and love.
The take home for all is that no
volcano is safe at all. The right conditions will trigger a cascade
of chambers releasing in series and bathing the countryside with ash
over a long period of time. History is only a suggestion that failed
in every major volcano which is why folks lived nearby.
The good news however, is that a multi
chamber blow out puts the volcano to sleep for a long time.
Iceland Volcano
Eruption Caused By Chain Reaction
November 30, 2012
According to NBC
News, after nearly two centuries of dormancy,
Eyjafjallajökull (AYA-feeyapla-yurkul) erupted many times over the
course of 10 weeks. The eruptions spewed a huge plume of ash that
caused extraordinary lightning displays, colored sunsets a fiery red
across much of Europe, and forced widespread flight cancellations for
days.
The eruptions began in
2010 when a fissure opened on the flank of Eyjafjallajökull in
March, revealing that it was inflating with magma. An explosion then
burst from the volcano’s summit in April, and three more major
explosions from Eyjafjallajökull rocked Iceland in May.
Analysis of material
spewed from the explosions suggests each explosion involved separate
chambers loaded with magma of distinct ages and compositions.
To learn more about
what caused this spate of eruptions, the researchers analyzed swarms
of microearthquakes during the outbursts. The data suggests that the
first explosion was rooted in a magma chamber about 3 miles (5
kilometers) below the surface, while the three later explosions
stemmed from magma chambers at depths of about 7 miles (11.5 km), 12
miles (19 km) and 15 miles (24 km).
Interestingly, the
researchers found that microearthquakes apparently occurred at
greater depths with each outburst. Researchers now suggest that the
series of eruptions was due to a “decompression wave” that
essentially rippled downward, upsetting the volcano’s plumbing.
The initial explosion
spewed a massive amount of magma and melted about 650 feet (200
meters) of ice. The researchers suggest this relieved a great deal of
pressure exerted from Eyjafjallajökull’s summit on its innards.
This drop in pressure from above caused a magma chamber slightly
lower down to begin inflating. When this led to an explosion, this
liberated magma in another chamber slightly lower down, and created a
cascade through successively lower chambers.
Jon Tarasewicz, a
geophysicist at the University of Cambridge in England said:
“It’s novel to
have been able to match the deep seismic observations to big changes
in the eruption rate at the surface. In this case, it seems the
volcanic plumbing system at depth responded to changes near the
surface, rather than vice versa.”
Tarasewicz continued
by saying:
“There are several
examples around the world of volcanoes that are thought to have more
than one magma chamber, stacked at different depths beneath the
volcano. Understanding the pressure linkage and feedback between
different magma storage reservoirs may help us to understand why
some volcanoes like Eyjafjallajökull have prolonged eruptions with
episodic surges in eruption rate.”
Although this research
could yield insights on the magma underlying a volcano and how it
might behave, Tarasewicz cautioned, “we are still not in a position
to be able to predict accurately in advance when, or if, a volcano is
going to erupt.”
The scientists
detailed their findings online October 13 in the journal Geophysical
Research
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