THE GEOMETRIC RELATIONSHIP BETWEEN HOT-SPOTS AND SEAMOUNTS - IMPLICATIONS FOR PACIFIC HOT-SPOTS

Hot spots and the seamounts produced by them provide both geometric an d temporal evidence for changes in absolute plate motion. The main lim itation in using hot-spot-produced seamounts in plate tectonic reconst ructions arises from the multiple sources of error and ambiguity that plague radiometric age estimates. In particular, unless the hot spot h as maintained a steady and voluminous flux rate over long periods of t ime, the exact location of a hot spot (which represents the zero age o rigin along the hot spot trail) is poorly known. Here, we discuss a un ique geometric relationship between a hot spot and the seamounts produ ced by it that we recently have discovered, i.e. hot-spot-produced sea mounts have seafloor crustal flow lines that intersect at the hot spot location. Furthermore, we obtain images of cumulative volcano amplitu des (CVA) by convolving seamount shapes with their flow lines; hot spo ts correspond to clear local maxima in this image and the amplitudes a re proportional to cumulative hot spot flux. This technique, dubbed 'h ot-spotting', allows us to determine hot spot locations based only on a set of seamount locations: no age information is required. We use th e hot-spotting technique to examine the Pacific plate hot spots in gen eral and the Bowie and Cobb hot spots in the Gulf of Alaska, in partic ular. We find that the Hawaii, Louisville, Caroline, Cobb, and Bowie h ot spots have clear representations in the CVA images, Rurutu and/or R arotonga are close to a large CVA high, while the other French Polynes ian hot spots in general exhibit a much more subdued and blurred expre ssion. We also conclude that the Cobb hot-spot plume may have been ent rained 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 recent ly. (C) 1998 Elsevier Science B.V. All rights reserved.