A theoretical model of hotspot volcanism: Control on volcanic spacing and patterns via magma dynamics and lithospheric stresses

Abstract

Many linear island chains are thought to be the result of the steady motion of the lithospheric plates over stationary hotspots. The occurrence of discrete, nearly regularly spaced volcanoes, rather than continuous ridges, are assumed to be caused by the interaction of flexural stresses (due to the volcanic loads) with magma percolation. A parameter study is performed on a simple model that incorporates these effects in addition to dike wall erosion. It is demonstrated that the strength of the erosional feedback determines whether the model generates discrete volcanoes or a continuous ridge. The intervolcanic spacing depends not only on the elastic thickness of the lithosphère but also on the magma pressure at the base of the lithosphère. The size of the eruptive region of the individual volcanoes is controlled by the elastic response of the lithosphère to magma overpressurization. If an initial off-axis edifice is introduced, the model is able to preserve this asymmetry and produce an alternating series of volcanoes. A small initial perturbation grows over time, resulting in double lines or wider patterns depending on the width of the magma source region. Single lines of volcanoes therefore indicate very narrow magma source regions. Copyright 2001 by the American Geophysical Union.