New Measurements Constrain Models of Mantle Upwelling Along a Midocean Ridge

JUL 01, 1998

Magma flowing upward to form fresh crust along the axis of plate spreading does not appear to come exclusively from a narrow zone directly beneath the axis. Rather, molten material is distributed along the ridge in a region more than 100 km wide and over 100 km deep. Moreover, the melt zone is centered to one side of the axis—beneath the faster moving plate.

DOI: 10.1063/1.882323

Barbara Goss Levi

It has long been known that as tectonic plates pull apart along the mid‐ocean ridge system, the mantle wells up to fill the gap. Partial melting of the mantle produces magma that percolates upward to the surface and solidifies into new crust within a few kilometers of the ridge. But the details of this process have been a mystery: Over what volume is the mantle melted to form this magma? What is the concentration of the melt? How connected are the pockets of molten material? To answer such questions, an international collaboration designed the Mantle Electromagnetic and Tomography (MELT) experiment, placing seismometers, electrometers and magnetometers on the ocean floor to span the midocean ridge known as the East Pacific Rise (see figure below). After several years of gathering and analyzing data, members of the collaboration presented their results at the Boston meeting of the American Geophysical Union at the end of May.