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Rambling and rumbling on an island volcano
Rambling and rumbling on an island volcano
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Lush tropical forests on the Samoan island of Ta'u. (Photo by Rhea Workman, WHOI) |
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GPS
locations on Ta'u Island, Samoa. |
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WHOI graduate student Rhea Workman explains her work on Volcanism to students on Ta'u. (Photo by Stan Hart) |
The Samoan island of Ta’u is a tropical paradise, but Rhea Workman
knows it was created by an undersea volcano that is still active. Ta’u’s central volcano was formerly dome-shaped, but one of its sides
collapsed in landslides that cast debris all the way onto the seafloor. The landslides left a steep escarpment, which is primed for further catastrophic landslidesand possibly tsunamisespecially if it is disturbed by movements inside the volcano.
Within a volcano’s underlying magma chamber, magma or gas continually surges or subsides, inflating, deflating, and deforming the volcano’s surface. These deformations are usually tiny, but they can be measured to evaluate what’s going on inside the volcano and predict whether it might erupt.
Workman, a graduate student in the WHOI Geology and Geophysics
Department, wanted to assess Ta’u’s volcano and landslide
hazard potential by measuring the volcano’s subtle motions
with Global Positioning Satellite receivers, which can measure
ground-motion changes within 1 centimeter. She organized an
expedition, conscripting GPS equipment and fellow MIT/WHOI
Joint Program students. In 2002, they installed GPS benchmarks
(middle image) throughout the island and took GPS measurements.
In 2004, Workman returned to re-measure the benchmarks, also
taking time to explain her research at local schools (bottom
image).
Since her return, Workman scrambled to complete and defend her
Ph.D. dissertation on March 16. Dr. Workman will now analyze and
compare her GPS measurements to see if she can detect telltale ground
motion on Ta’u.
This research was supported by a grant from the Robert
H. Cole Endowed Ocean Ventures Fund.
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