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By Gari Mayberry - USGS Volcanic Activity Report
Scientists
from NOAA used the T-phase Monitoring System to search for
megaplumes from a possible eruption of the Jackson Segment
of the Gorda Ridge that began on 3 April. They did not find
evidence of a plume after collecting 25 vertical hydrographic
casts during 11-16 April. Two bottom camera tows were also
collected, but the film had not been developed at the time
of this report. By 11 April seismic activity was at very
low levels, possibly below the detection threshold of the
T-phase Monitoring System.
Background.
The Jackson segment of the Gorda Ridge lies immediately
SSW of the North Gorda segment, about 200 km W of the southern
Oregon coast. A submarine lava flow was erupted in February-March
1996, near the center of the nearby North Gorda Ridge segment.
The eruption was initially detected through acoustic T-waves
from a seismic swarm and the emission of large thermal plumes.
In April submarine cameras revealed new lava flows about
100-200 m wide along a fissure that was at least 3.5 km
long. A seismic swarm of uncertain origin also occurred
at this location in January 1998.
Source:
National Oceanic and Atmospheric Administration http://www.pmel.noaa.gov/vents/acoustics/seismicity/nepac/gordaridge01.html
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