Magnetotelluric Experiment probes deep physical state of southeastern United States

A combined continental‐oceanic magnetotelluric (MT) transect of the southern Appalachians orogenic belt has been completed that spans nearly 600 km on land and extends over 1000 km offshore beneath the Atlantic Ocean (Figure 1). The study is revealing the long‐term changes in the lithosphere that occur as active subduction regimes degenerate to fossil regimes, and tests the degree to which the latter are modified by subsequent extension. The electrical resistivity structure of active subduction has been examined by several researchers in recent years [Wannamaker and Hohmann, 1991; Jones, 1993], but here is the first thorough examination of a currently passive, former convergent margin.