The Soufrière Hills, a volcano on the island of Montserrat, in the
Lesser Antilles island chain in the Caribbean Sea, has been active
since 1995. The most recent eruptive phase of the volcano began with a
short swarm of volcano-tectonic earthquakes—earthquakes thought to be
caused by movement of magma beneath a volcano—on October 4, 2009,
followed by a series of ash-venting events that have continued through
October 13, 2009. These venting events create plumes that can deposit ash at significant distances from the volcano. In addition to ash plumes, pyroclastic flows and lava dome growth have been reported as part of the current eruptive activity.
This oblique astronaut photograph from
the International Space Station (ISS) captures a white-to-gray ash and
steam plume extending westwards from the volcano on October 11, 2009.
Oblique images are taken by astronauts looking out from the ISS at an
angle, rather than looking straight downward toward the Earth (a
perspective called a nadir view), as is
common with most remotely sensed data from satellites. An oblique view
gives the scene a more three-dimension quality, and provides a look at
the vertical structure of the volcanic plume.
While much of the island is covered in green vegetation, gray
deposits that include pyroclastic flows and volcanic mudflows (lahars)
are visible extending from the volcano toward the coastline. When
compared to its extent in earlier views,
the volcanic debris has filled in more of the eastern coastline. Urban
areas are visible in the northern and western portions of the island;
they are recognizable by linear street patterns and the presence of
bright building rooftops. The silver-gray appearance of the Caribbean
Sea surface is due to sunglint, which is
the mirror-like reflection of sunlight off the water surface back
towards the handheld camera onboard the ISS. The sunglint highlights
surface wave patterns around the island.
Astronaut photograph ISS021-E-5555
was acquired on October 11, 2009, with a Nikon D2Xs digital camera
fitted with a 400 mm lens, and is provided by the ISS Crew Earth
Observations experiment and Image Science & Analysis Laboratory,
Johnson Space Center. The image was taken by the Expedition 21 crew. The image in this article has been cropped and enhanced to improve contrast. Lens artifacts have been removed. The International Space Station Program
supports the laboratory to help astronauts take pictures of Earth that
will be of the greatest value to scientists and the public and to make
those images freely available on the Internet. Additional images taken
by astronauts and cosmonauts can be viewed at the NASA/JSC Gateway to Astronaut Photography of Earth. Caption by William L. Stefanov, NASA-JSC.