Quarterdeck 3.3

Part 2 (conclusion)
TAMU-Squared and related geophysical studies of the East Pacific Rise


By Thomas W. Hilde

. . .Continued from part 1

Our goals include relating the observed variations in seafloor geology, structure and bathymetry to evolutionary stages in the processes of magmatizm along the ridge, to determine which segments are presently in constructive stages, the time scale for ridge constructive processes and, by comparative analysis of FAST Ridge Expedition data with that data previously collected, whether ridge segments have undergone inflation or deflation in the last few years.

[242K] Three-dimensional detail map of the section of the East Pacific Rise under study.

This super-fast spreading segment of EPR offers a great opportunity to study the fundamental aspects of crustal origin at oceanic spreading centers. The full spreading rate along this ridge segment is 150-160 millimeters per year. Previous studies have revealed an extremely narrow, elevated ridge axis, hydrothermal venting temperatures of about 400°C, magma chambers as shallow as about 900 meters and fresh, glassy basalt at many submersible dive locations. [TAMU]-squared is showing us the distribution and variation in tectonic and volcanic activity along the ridge. The data quality has been excellent-the images are like photographs. So far, we have observed that overlapping spreading exists at various scales all along the ridge. We have found numerous axial rifts, extensive volcanic flows on the ridge flanks and mammoth off-ridge lava flows. Normal faulting is most extensively developed at the base of the elevated two- to four-mile-wide axial ridge. Apparently the axial ridge crest is sufficiently hot and plastic so that brittle faulting does not become the dominant tectonic expression until the newly formed crust has moved a mile or two away from the ridge axis.

In order to guide our mapping and to get started with our data analysis, we are processing the data aboard ship as it is acquired. The [TAMU]-squared system displays both the imagery and bathy-metry in real-time as waterfall displays on computer monitors and strip recorders. Additionally, the digital data are recorded to high density tape for archiving, and transferred via network to an off-line Silicon Graphics work-station for post-acquisition processing. By the time we get to the Galapagos Islands, we should have mosaics of the imagery, contour images and three-dimensional images for much of the ridge.

Assuming no equipment failures during the remainder of the expedition we expect return with a data set that will provide new insights into the processes and structure of this super-fast spreading segment of the East Pacific Rise.


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Oceanography, Texas A&M University

rshatto@ocean.tamu.edu

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Updated January 8, 1996