Abstract

President's anniversary address 1982

The preservation of volcanoes—never more than partial—involves a complex interaction of processes and these operate over periods of time which are often undervalued. From a review of the relative rates of these processes it seems that short-lived structures such as Surtseyan ash-rings may be preserved, albeit in modified form, around their whole circumference. For larger composite volcanoes, however, growth and remoulding by activity is balanced by penecontemporaneous and later erosion in such a way that the central and most of the proximal zones are likely to be removed before they can be buried either by transported volcaniclastic or regional epiclastic sediments. Even the preservation of distal zones may be asymmetrical. A one-sided hinge-line subsidence-sedimentation model is therefore suggested to explain the elongate lens-shaped aspects of the many extrusive piles known to lie approximately concordantly within stratigraphic sequences formed in both continental and littoral environments.

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