In the first major eruption since 1992, Etna, Europe’s most active volcano,
is spewing out lava, ash, smoke and rocks in a pyrotechnic display which is
threatening nearby towns and infrastructure. Instruments on board ESA’s
European Remote Sensing satellite ERS-2 are carefully monitoring the
volcano’s activity.
Although residents of the nearby village of Nicolosi in Sicily, Italy, are
used to the 3310-metre volcano springing into life every few months, this is
the first major eruption since 1992, when for the first time explosives were
used to deviate the flow of lava away from populated areas.
For more than two weeks the Italian authorities have been working day and
night, trying to divert the flow of lava which is rolling down Etna’s slopes
at speeds which can reach 2 metres per minute. A Herculean task which has
to be repeated, as quickly as possible, each time the lava overruns the
man-made barriers.
Instruments on board ERS-2 monitor the volcano’s movements, temperature
and gas emissions. The most recent images from the Global Ozone Monitoring
Experiment (GOME) instruments, which provide information on trace gas levels
in the atmosphere, show that the level of sulphur dioxide released by the
volcano are ten times higher than normal. This area of high concentration
can be found up to 1000 km away and covers an area almost the size of
Germany.
Another instrument on board ERS-2, known as the Along Track Scanning
Radiometer (ATSR), measures the temperature of the Earth’s surface and
clearly shows the plume of smoke arising from the volcano’s crater. By
combining images from ATSR and GOME it can be seen that the visible plume
of the volcano, consisting of water vapour and dust, has a far smaller
extent than the chemical pollution in the atmosphere.
Monitoring Etna is not just a one-off operation. It is now over 10 years
since ESA’s ERS satellites first began providing environmental data.
Instruments on board the ERS satellite constantly keep watch over the
Earth and provide precise and timely environmental data for users. In
fact, the Synthetic Aperture Radar (SAR) data provided by ERS-1 and ERS-2
have been a new source of information for volcanologists who use a complex
technique called SAR interferometry, to track vertical movements of the
volcano with a centimetre precision.
Volcanoes are unpredictable and Etna is no exception. Says Wolfgang Lengert,
ESA ERS Mission Coordinator, “no-one can say for sure when this latest
eruption will stop but the valuable data supplied by 10 years of SAR data
from the ERS satellites is one of the tools that will be used to better
understand this volcano.”
Once Envisat, ESA’s newest satellite for environment monitoring, is
launched in a few months time, vulcanologists will have yet more and
better data to add to that already supplied by ERS, to help them with
their studies of Mount Etna.
More information
* ERS 1 and 2
http://www.esa.it/export/esaCP/GGGWBR8RVDC_Benefits_0.html
* ERS achievements
http://www.esa.it/export/esaCP/GGGL0Z7RVDC_Protecting_0.html
* ERS: Etna
http://uranus.esrin.esa.it/ers/article_archive/#gome
Related Links
* ERS homepage
* ESA Earth Watching: Etna
http://earth.esa.int/ew/pl_etna.htm
* ERS Instruments
http://earth.esa.int/ers/instruments
IMAGE CAPTIONS:
[Image 1:
http://www.esa.it/export/esaCP/ESAJRC1VMOC_index_1.html]
Italian volcanologist, Daniele Lodato, checks the eruption frequency from
Mount Etna, Europe’s largest active volcano, as plumes of smoke spews from
one of its openings, near Nicolosi, Sicily, Tuesday, July 24, 2001. Ashes
from the restive Mount Etna continue to rain down and the nearby airport of
Catania has had to close several times because of the black volcanic ash and
dust on the runway. Photo: AP Photo/Fabrizio Villa.
[Image 2:
http://www.esa.it/export/esaCP/ESAJRC1VMOC_index_1.html#subhead1]
Scientists of the German Space Agency (DLR) in Oberpfaffenhofen have been
monitoring the eruptions of the Etna volcano since Mid of July with the GOME
instrument on board ERS-2. The satellite data show a region southeast of
Sicily, where the atmosphere is polluted with a concentration of sulphur
dioxide (S02) up to 10 times higher than normal. To give an idea of the
scale, the size of the area of dense concentration is close in size to that
of Germany.
[Image 3:
http://www.esa.it/export/esaCP/ESAJRC1VMOC_index_1.html#subhead2]
The image shows details using the infrared and 11 micron channel. The plume
of smoke is very evident in the image due to the temperature difference
between the smoke and the sea. Interestingly, the smoke is cooler than the
sea — much as the wake that follows a jet aircraft.
[Image 4:
http://www.esa.it/export/esaCP/ESAJRC1VMOC_index_1.html#subhead3]
26.07.01 A view of Mt. Etna showing the new lava stream that is worrying
experts for the small town of Nicolosi, Sicily, 4 kilometers below. Sicily’s
Mount Etna, 3310 metres high, surprised experts who were predicting the
worst was over. After appearing to calm down for a day the volcano began to
erupt violently Wednesday afternoon and evening. Photo: AP Photo/Pier Paolo
Cito.
