song of the volcano sent across the Atlantic from Montserrat
don't only erupt they sing, and in a new development
by geophysicists at the University of Leeds, the sounds
or seismic tremor made by a volcano thousands of miles
across the Atlantic will be transmitted directly to Leeds,
where they will be analysed to show the minute changes
in pressure which foretell an imminent eruption.
60 volcanoes are active each year around the world, with
many others erupting unobserved on the ocean floor, and
accurate predictions of volcanic activity is vital to
based on sound as well as movement should improve predictions
of when a volcano might erupt, although scientists are
already very close to achieving accuracy in terms of time.
But more importantly, it may help in forecasting the size
and type of eruption, especially in volcanoes which create
a magma dome and release the most deadly weapon a volcano
has: pyroclastic flows made up of lava full of hot rocks
and gas which quickly expands, travelling much faster
than normal lava flows.
monitoring the ground deformation and seismic signals
on a volcano, geophysicist Dr Jurgen Neuberg (pictured
below) of the school of earth sciences has found that
it is possible to identify certain seismic events which
indicate pressure within the volcano before it erupts.
His approach is novel in that he uses broadbad seismic
arrays rather than standard seismographs to measure volcanic
activity. He can then analyse the sound made by the pressure
changes within the volcanic system, and decompose it to
show the harmonic content.
explains: "Imagine someone clapping their hands close
to a harp. The clapping will cause all the harp strings
to vibrate to different degrees, and this whole range
of frequencies is what we analyse in relation to the volcano."
did the pilot test on the Stromboli volcano near Sicily,
which has a minor eruption every thirty minutes, so it's
excellent for trying out new techniques. It was fantastic
as well for undergraduate students to be part of ground-breaking
research the first successful broadband array.
A broadband array shows the full spectra of sound which
the volcano makes. It's like looking at a picture directly,
whereas a traditional seismometer is like looking at it
through blue glass."
Neuberg is focusing much of his research on Montserrat
(see pictures, above and below), where, after several
hundred years of lying dormant, the Soufriere Hills volcano
erupted in June 1997. Four to five million cubic metres
of lava and rocks came down in a matter of minutes spreading
across four square kilometres on the east side of the
island, covering the whole town of Plymouth under ash
and mud and claiming twenty casualties (see picture
added: "Although most people talk of volcanoes erupting,
the volcano on Montserrat actually 'collapsed'. The magma
in the volcano is very viscous, and it wells up under
the surface to form a bulge or dome on the side of the
mountain. This dome is unstable and is weakened by hydrothermal
alteration of the rock. Eventually the surface gives way
under its own weight, releasing lava and producing pyroclastic
1997, the dome has continued to form and collapse, releasing
pyroclastic flows on a regular basis. In 1998 the cycle
appeared to stop, but the dome has since begun growing
again. The process could go on for 10 years.
very spooky to go to Plymouth now," Dr Neuberg recalls.
"Everywhere is white and light grey with ash, and although
most of the buildings are standing, the first two floors
are filled with ash and mud. It's very sobering, and makes
you realise how important it is to be able to predict
these events as accurately as possible."
part of a European project, MULTIMO, which he coordinates,
Dr Neuberg plans to drill bore holes on Montserrat and
equip them with a seismometer, a tiltmeter and a strainmeter.
These will link to an observatory and then via a direct
internet link to Leeds allowing scientists at the
University to see the output from the bore holes simultaneously
online. The advantage of bore holes to surface measurements
is that they are away from surface noise, and so can offer
a clearer picture of the volcano without disturbances.
Drilling for the bore holes will begin later this year.
a team of researchers, he is also modelling the physical
conditions inside the volcano, using computer simulation
to reproduce the seismic wave propagation in gas charged
magma. He hopes this will help to understand the signals
and how they link to magma properties. "Scientists are
already close to predicting when a volcano will erupt,"
says Dr Neuberg.
challenge now is to predict the size and nature of that
eruption. This is the only way in which we will avoid
the loss of life we saw on Montserrat, and have seen in
similar, predicted eruptions such as that on St Helens
in the USA, where several scientists died.
can't control volcanoes our only hope is to understand