Introduction

Various classifications of coasts have been attempted in the literature, in some cases inspired by the plate tectonics model (e.g. Inmam & Nordstrom, 1971). According to Rice (1941) and to the American Geological Institute (1960), the term ‘tectonic’ is defined in a very wide sense, ‘designating the rock structure and external forms resulting from the deformation of the earth's crust’. This definition implies that certain processes, which are not always considered as ‘tectonic’, must also be taken into account. It is now widely accepted that phenomena like glacioisostasy and hydroisostasy have produced a vertical deformation of the earth's crust in virtually all coastal areas over the last 20 ka (Clark, Farrell & Peltier, 1978). Moreover, sediment deposition near coasts and especially in delta areas contributes, together with erosion processes and volcanic eruptions, to the modification of loads exerted on the earth's crust, causing additional vertical deformation (see Chapter 3). Consequently, all the coasts of the world can be considered as more or less tectonic and none are vertically stable. Instead of proposing a new classification, the present chapter aims therefore to identify various kinds of vertical movement which may affect any of the types of coast considered elsewhere in this volume, with, however, more emphasis on seismo-tectonic processes. Certain effects of vertical movements on coastal evolution are also considered.