The geometric relationship between hot spots and seamounts: implications for Pacific hot spots

Hot spots and the seamounts produced by them provide both geometric and temporal evidence for changes in absolute plate motion. The main limitation in using hot-spot-produced seamounts in plate tectonic reconstructions arises from the multiple sources of error and ambiguity that plague radiometric age estimates. In particular, unless the hot spot has maintained a steady and voluminous flux rate over long periods of time, the exact location of a hot spot (which represents the zero age origin along the hot spot trail) is poorly known. Here, we discuss a unique geometric relationship between a hot spot and the seamounts produced by it that we recently have discovered, i.e. hot-spot-produced seamounts have seafloor crustal flow lines that intersect at the hot spot location. Furthermore, we obtain images of cumulative volcano amplitudes (CVA) by convolving seamount shapes with their flow lines; hot spots correspond to clear local maxima in this image and the amplitudes are proportional to cumulative hot spot flux. This technique, dubbed 'hot-spotting', allows us to determine hot spot locations based only on a set of seamount locations: no age information is required. We use the hot-spotting technique to examine the Pacific plate hot spots in general and the Bowie and Cobb hot spots in the Gulf of Alaska, in particular. We find that the Hawaii, Louisville, Caroline, Cobb, and Bowie hot spots have clear representations in the CVA images, Rurutu and/or Rarotonga are close to a large CVA high, while the other French Polynesian hot spots in general exhibit a much more subdued and blurred expression. We also conclude that the Cobb hot-spot plume may have been entrained by the Juan de Fuca Ridge about 2 Ma ago, or, alternatively, is in a waning phase and cannot penetrate Juan de Fuca plate lithosphere. The Bowie hot spot appears to have encountered the ridge more recently. (C) 1998 Elsevier Science B.V. All rights reserved.