Submitted to Science 02/28/00

• Main Authors: William R. Keller, Don L. Anderson, Robert W. Clayton
• Other Authors: The Pennsylvania State University CiteSeerX Archives
• Format: Text
• Language: English
• Subjects: Iceland
• Online Access: http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.556.9585; http://www.gps.caltech.edu/~dla/iceland.pdf

The locations of volcanic islands may be controlled by thin or extending parts of the lithosphere over a partially molten asthenosphere (1, 2), by edge effects near the boundaries of thick cratonic lithosphere (3), or by narrow jets of hot mantle rising from deep within the mantle (4-6). Many hotspots are found on or near ridges, at lithospheric discontinuities, or in extensional environments, so high resolution seismic images are required to determine whether it is lithospheric structure, stresses in the lithosphere, or the deep mantle that is the controlling factor for the location of active volcanoes. In this study, we perform a simple experiment in which we use basic geometrical arguments and idealized experimental parameters in order to understand the resolution of tomographic images of the upper 400 km of the mantle under Iceland. Our results indicate that a narrow, deep seated mantle plume is not required in order to explain the observed travel time delays. Results of tomographic inversions are often viewed as unique; however, recent seismic studies of the Icelandic Hotspot have illustrated the non-unique nature of these models. The geometry of plumes in laboratory and computer simulations is a narrow cylinder capped by a bulbous head that flattens beneath the lithosphere, giving an overall mushroom shape to the upwelling (7-9). Deep mantle upwellings are also expected to broaden beneath the 650 km endothermic phase change. On the other hand, the geometry of upwellings driven by