MEDIA RELEASE: 24 MARCH 2006
MAGMA IMPLICATED IN RAOUL ERUPTION, SCIENTISTS SAY
Scientists now believe the 17 March eruption at Raoul Island was caused by new magma rising to a shallow depth beneath the island, GNS Science said today.
Previously it was unclear if the eruption was caused by movement of magma or by instability in the hydrothermal system beneath the island.
Satellite images taken after the eruption have confirmed that the volcano belched 200 tonnes of sulphur dioxide during the eruption and in the following five hours.
" This confirms the involvement of magmatic gases in the eruption, and the presence of degassing magma within the volcano," said GNS Science Volcano Surveillance Co-ordinator Brad Scott.
Subsequent satellite observations have not detected sulphur dioxide, most likely owing to the absorption of this gas by Green Lake and by the island's hydrothermal system.
The satellite information was supplied by the University of Maryland and NASA.
Earthquake activity over the past few days at or near the island has continued to decline, Mr Scott said.
There are now only five to 10 earthquakes a day, most of which are probably too small to be felt on the island.
Scientists now consider the likelihood of future magmatic activity higher than originally thought.
" However, the lack of earthquakes that clearly signal movement of magma suggests that the volume of magma at shallow depth beneath the island may be relatively small," Mr Scott said.
"Also, the steady decline of seismic activity since the eruption suggests that magma may not be continuing to move up to shallow depths."
Scientists would continue to monitor earthquake activity at Raoul Island .
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