In the Pacific Northwest, the Juan de Fuca plate, a remnant of the Farallon plate, continues to subduct beneath the North American continent (Figure 2.47). To the east of the Cascadia subduction zone lies the Yellowstone hotspot track. The origins of this track can be traced back to the voluminous basaltic outpourings of the Columbia Plateau around 17 Ma (Watkins and Baksi, 1974; Christiansen and McKee, 1978). If these basalts are the result of a large melting anomaly rising through the mantle to the base of the North America continent, such as a mantle plume head, the anomaly would need to punch through the subducting Juan de Fuca slab. Here, we use teleseismic body wave travel time tomography to investigate the fate of the subducted slab and its possible interaction with a plume head.

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