10 April 2003

MBARI geologist describes close-up views of deep-sea ridges

This week, MBARI geologist Debra Stakes will take part in a press conference discussing new technologies that allow detailed mapping and exploration of the deep sea floor. Her presentation at the 2003 EGS-AGU-EUG Joint Assembly in Nice, France will describe how high-resolution bathymetric maps were combined with detailed geologic surveys using a remotely operated vehicle (ROV) along the Cleft Segment of the Southern Juan de Fuca Ridge. According to Stakes, "With the ROV and accurate bottom maps, we can 'walk around' the sea floor much as a geologist would do on land, carrying a topographic map and air photos." Using the ROV to go "off the beaten path," Stakes and her colleagues discovered that recent volcanic activity is not confined to undersea ridges themselves, as was once believed, but can occur in adjacent areas as well.

Side-scan sonar image of the sea floor along the Cleft Segment of the Juan de Fuca Ridge (an active sea-floor spreading center off the coast of Oregon). The circled numbers indicate a few of the areas that were explored using the remotely operated vehicle (ROV) Tiburon. Typical examples of the underwater "landscape" in each area are shown in the photos below.

1) Along the main ridge axis, geologists expected to find recent lava flows forming massive sheets. However, ROV explorations showed that in many places these sheet flows are overlain by even more recent, ropey (pahoehoe) lava, as shown in this photo.

2) A few kilometers to the west of the ridge axis, geologists expected to find only flat sheets of older lava. Instead they found relatively young, rounded pillow lavas that had apparently emerged from cracks and faults, to flow over and around the original sheet flows.

3) Even farther from the main ridge axis, where the crust was presumed to be cold and dead, ROV dives showed many low-temperature hydrothermal vents releasing water rich in iron and manganese. The orange crusts that rim these vents are formed by iron-loving bacteria.

Press Conference:

New closeup views of three mid-ocean ridges
Date/Time: Thursday, 10 April; 09:00
Location: Athena Theatre lobby		 Poster:

D. S. Stakes, M. R. Perfit, C. G. Wheat,
T. M. Ramirez, R. A. Koski, J. R. Hein
PO 158: Evidence of Off-Axis Volcanism and Hydrothermal Venting along the Cleft Segment of the Southern Juan de Fuca Ridge

For more information and additional images, contact: Debbie Meyer (831) 775-1807, pressroom@mbari.org