El Reventador
SeaWiFS image of the eruption plume fromEl Reventador
volcano, Ecuador, acquired November 3, 2002.Clickthe image for a larger
version.
The first Science Focus! article that provided SeaWiFS images of
volcanic activity was appropriately entitled SeaWiFSViews Volcanoes.About eighteen months
have passed since this article was published on the World Wide Web, and SeaWiFS
has captured more striking images of volcanic eruptions around the world.Some
of these eruptions caughtground observers by surprise, and SeaWiFS was
fortunately positioned toview these eruptions from space.
The image above is of an eruption of the El Reventador volcano in Ecuador,
acquired on November 3, 2002. The ash plume of the volcano is emerging above
the clouds that rise over the Andean highlands.Ash from this eruptionfell
heavily on the capital city of Quito located 60 miles southeast of the
volcano.
Reventador, Ecuador has images of the November 3 eruption and subsequent
activity.
Aerial
view of Ecuadorean volcano Reventador erupting
Shiveluch
Eruption plume from an eruption of Shiveluch volcano (red
arrow) on the Kamchatka peninsula, Russia, acquired August 30, 2000.Click on
the image for a larger version showing most of the Kamchatka
peninsula.
One of the most remote volcanically-active regions in the world is Russia's
Kamchatka peninsula.Shiveluch volcano has been rumbling there for several
months.Cloud cover in this frigid northern region is persistent, so this
image of an ash plume from an eruption of Shiveluch was a very lucky "catch".
Kamchatkan, Aleutian, and Alaskan volcanoes pose a definite danger to
aircraft, as the flight paths of many trans-Pacific flights from the United
States to Asian destinations pass over this area frequently. On December 15,
1989, a KLM747 jet encountered an ash plume from an eruption of Redoubt
volcano on theAlaska Peninsula.The ash entered the jet engines, melted, and
causedthe shutdown of all four engines.The crew was able to restart one
enginejust seconds before the plane crashed. Due to the ongoing threat to
aircraft posed by ash plumes from volcanic eruptions, the Alaska Volcano Observatory monitors the
activity of Alaskan and Kamchatkan volcanoesand posts alerts when volcanic
eruptions are threatening or in progress.
Monitoring of Shiveluch with video clips (IVGG, Russia)
Kamchatkan Volcanic Eruption Response Team (KVERT) Fact Sheet
Mount Etna
SeaWiFS image of ash plume from the flank eruption of Mt.Etna,
Sicily (center of image) acquired on July 22, 2001.Also note haze from
Saharan dust over the Mediterranean Sea on the western side of the
image.
The massive volcano Mt. Etna on the island of Sicily in the Mediterranean
Seais so frequently active that it rarely catches volcanologists by surprise,
but the flank eruption that began on July 18, 2001 actually did.Etna had been
providing spectacular activity from its summit craters for several years, and
that activity was relatively safe to watch and popular with tourists.
Flank eruptions, where the activity takes place on the sides of the volcano,
are a different matter. This flank eruption of Etna created several new
cinder cones and lava flows, and the lava flows damaged or destroyed parts of
a popular tourist center despite efforts to divert them. In addition, the
heavy plumes of ash forced the closure of the local airport in Catania several
times.
After taking a break for several months, Etna came to life again late in
October 2002 with an even more powerful flank eruption that continued into
January 2003.
Italy's Volcanoes:The Cradle of
Volcanology has voluminous information on Etna and other Italian volcanoes.
Stromboli
On-Line'sEtna section has marvelous photographs and videos of Etna's
activity.
Mount Oyama
SeaWiFS image of eruption plume from Mt. Oyama, Japan,
acquired on August 19, 2000.
Japan's Mount Oyama is rarely a threat to the main islands of Japan, because
it's aa considerable distance away.In fact, the spiraling low-pressure
weather systemlocated to the northeast of Japan in this image was probably
more of a concern thanthe ash from the eruption of Mt. Oyama to the south.
However, the residents of Miyakejima Island, where Mount Oyama is located,
were very concerned about this explosion, as was the government of Japan.So
concerned,in fact, that the the island's entire population of about 3,800
inhabitants weresubsequently evacuated. In addition to the ash cloud, rain
created the dangerouspossibility oflahars (floods of volcanic ash mixed
with water). The former residentsof Miyakejima Island have not yet returned.
Mount
Oyama, Miyakejima Island, Japan
Mount Oyama Erupts! is a PDF poster featuring a three-dimensional view of
the Mount Oyama eruption acquired by the Multi-angle Imaging Spectroradiometer
(MISR) in orbit on the Terra Earth Observing System satellite.
Soufriere Hills, Mont Pelee, La Soufriere
SeaWiFS image of an ash plume from Montserrat's Soufriere
Hills volcano, acquired on November 8, 1998.The small image shows aslightly
enlarged image excerpt to aid identification of the ash plume.
Finally, an image that the first "SeaWiFS Views Volcanoes" article missed.
The image above shows a small plume of ash drifting away from small Montserrat
Island in the Caribbean Sea.Like the residents of Miyakejima Island, many of
theresidents of once-idyllic Montserrat were forced to evacuate after the
Soufriere Hills volcano became active in 1995.Less than one-quarter of the
island's populationremains.
The third large island to the south of Montserrat (after butterfly-shaped
Guadaloupe and cloud-shrouded Dominica) is the island of Martinique.
Martinique also has a volcano, named Mont Pelee.The volcanoes on Martinique,
Montserrat, and Miyakejima all have a similar eruptive "style" in which a dome
of pasty, thicklava (andesite) grows slowly in the crater of the volcano.
This dome is unstable,and as it rises, parts of it can suddenly collapse,
triggering the fearsome volcanicphenomenon called a pyroclastic flow (or more
poetically, the nuee ardente or "glowing avalanche").Pyroclastic flows
are clouds of superheated gas and ash that flow down the mountainside at high
speed, lubricated by their own hot gas.Pyroclastic flows incinerate
everything that lies in their path.
On May 8, 1902, following weeks of activity, a powerful eruption from Mont
Pelee unleashed a pyroclastic flow that descended on the city of St. Pierre.
Nearly 30,000 people died within minutes.
At the bottom far right edge of the image, the island of Barbados can be
seen. West of Barbados is the island of St. Vincent, mostly covered with clouds
(the island of St. Lucia, north of St. Vincent and northwest of Barbados, is
largely cloud-free).In a strange linkage of events, La Soufriere volcano
on St. Vincent erupted only hours before Mont Pelee on May 8, 1902, and the
pyroclastic flows from La Soufriere killed approximately 1,800 people on
this tragic date.
Montserrat Volcano Observatory (slow to
load, features weekly activity updates)
Stromboli On-Line Montserrat section
Mt. Pelee, West Indies
So when volcanoes like Mont Pelee, Mt. Oyama, or Soufriere Hills growl,
smoke, and rumble, evacuations are definitely advisable.From its altitude of
705 km, SeaWiFS can provide a safe view from space.
Acknowledgements
We wish to thank the volcanologists and other researcherswho have provided
the Web pages and volcanic photographs andinformation utilized in this
Science Focus! article.
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