eruptions destroy ozone and create ‘mini-ozone holes’, according
to two new studies by researchers at the Universities of
Cambridge and Oxford.
The new research,
spearheaded by Dr Genevieve Millard at the Department of Earth
Sciences, University of Cambridge, discovered that volcanic
gases released during eruptions accelerate reactions that lead
to ozone destruction. The researchers found that even relatively
small volcanic eruptions can destroy ozone and create localised
‘holes’ in the stratosphere.
scientists had concentrated on the climatic effects of the tiny
particles of volcanic sulphate created from the sulphur dioxide
gas emitted during an eruption. For the first time, analysing
data from a 2000 eruption of the Hekla volcano, Iceland, the
researchers discovered that volcanic gases may also lead to the
formation of ice and nitric acid particles. This is a critical
finding as these particles ‘switch on’ volcanic chlorine gases,
accelerating reactions that lead to ozone destruction.
Dr Millard said,
“We have shown for the first time that volcanic eruptions which
penetrate the stratosphere can lead to the formation of the type
of clouds that promote reactions with volcanic chlorine gases -
gases that destroy stratospheric ozone and lead to the formation
of ‘mini-ozone holes’.”
The ozone losses
due to the small eruption at Hekla lasted for about two weeks,
and eventually returned to normal levels. This is the first time
that people have observed the complete removal of local ozone
following a volcanic eruption.
“Now we want to
find out what might happen to the ozone layer after a much
larger eruption,” said Dr David Pyle, University of Oxford,
project coordinator. “For example, is there significant loss of
ozone and increased ultra-violet radiation at low latitudes
following large explosive eruptions? We want to understand this,
so that we can have a better picture both of what might have
happened in the past, and of what may happen in the future”.