The MELT Seismic Team

The Mantle Electromagnetic and Tomography (MELT) Experiment was designed to distinguish between competing models of magma generation beneath mid-ocean ridges. Seismological observations demonstrate that basaltic melt is present beneath the East Pacific Rise spreading center in a broad region several hundred kilometers across and extending to depths greater than 100 kilometers, not just in a narrow region of high melt concentration beneath the spreading center, as predicted by some models. The structure of the ridge system is strongly asymmetric: mantle densities and seismic velocities are lower and seismic anisotropy is stronger to the west of the rise axis.

D. W. Forsyth* and D. S. Scheirer, Department of Geological Sciences, Brown University, Providence, RI 02912, USA.
S. C. Webb, L. M. Dorman, J. A. Orcutt, A. J. Harding, D. K. Blackman, J. Phipps Morgan, Scripps Institution of Oceanography, University of California, San Diego, La Jolla, CA 92093, USA.
R. S. Detrick, Y. Shen, C. J. Wolfe, J. P. Canales, Woods Hole Oceanographic Institution, Woods Hole, MA 02543, USA.
D. R. Toomey, Department of Geological Sciences, University of Oregon, Eugene, OR 97403, USA.
A. F. Sheehan, Department of Geological Sciences and Cooperative Institute for Research in Environmental Sciences (CIRES), University of Colorado, Boulder, CO 80309, USA.
S. C. Solomon, Department of Terrestrial Magnetism, Carnegie Institution of Washington, Washington, DC 20015, USA.
W. S. D. Wilcock, University of Washington, School of Oceanography, Seattle, WA 98195, USA.

Volume 280, Number 5367 Issue of 22 May 1998, pp. 1215 - 1218
©1998 by The American Association for the Advancement of Science.