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Most of the volcanic eruptions that occur on earth are located far from
view, on the bottom of the ocean, where seafloor spreading occurs, along
a vast mountain chain known as the Mid-Ocean Ridge. Due to the extreme
difficulty of making observations in this remote environment, only a
handful of volcanic eruptions have been directly observed. One of the
few locations where an eruption has been detected is the fast-spreading
East Pacific Rise at ~9°N. Here, instruments deployed to monitor the
region after an eruption in 1991, were fortuitously in place and
continued to operate through a second eruption in 2005-2006. In addition
to this documented history of volcanic eruptions, the region is also one
of vigorous venting of hot water from the seafloor, abundant
hydrothermal mineral deposits, and elaborate animal communities that
thrive in the absence of sunlight through chemosynthesis. Focused
investigations in this region over the past two decades have enabled us
to document how the system evolved between the two eruptions and to
construct views of the surface of this active seafloor volcano of
unprecedented detail.
In summer 2008, using modern techniques employed by the oil industry and
now available to the scientific research community for the first time,
we were able to image deep beneath this volcano to the magma reservoir
that lies 1.5 km under the seafloor. The aims of our study were to
better understand what triggers volcanic eruptions in this area and why
hydrothermal deposits form and animal communities thrive here. The
imaging technology (a multi-streamer seismic array) used in our study
allows us to determine the distribution and amount of magma trapped
within this magma reservoir in very fine detail and permits us to
directly link the hydrothermal communities and volcanic eruptions on the
seafloor with the underlying source of magma and heat deep within the
earth's crust. This presentation will focus on the history of volcanic
eruptions and hydrothermal activity at this site, and how modern seismic
techniques are used to reveal the inner workings of this active volcano. |
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