. Collected reprints / Atlantic Oceanographic and Meteorological Laboratories [and] Pacific Oceanographic Laboratories. Oceanography 15 Reprinted from ENCYCLOPEDIA OF GEOMORPHOLOGY, Reinhold, 1968 I WAVE BASE In principle, wave base is the downward limit to which waves can move bottom particles. As defined by Gulliver (1899, pp. 76-77), wave base determines the ultimate depth of a platform of marine abrasion. No particular depth was specified, but in recent years several workers have placed its effective depth at about 10 meters, perhaps ulti- mately about twice this (Dietz and M
. Collected reprints / Atlantic Oceanographic and Meteorological Laboratories [and] Pacific Oceanographic Laboratories. Oceanography 15 Reprinted from ENCYCLOPEDIA OF GEOMORPHOLOGY, Reinhold, 1968 I WAVE BASE In principle, wave base is the downward limit to which waves can move bottom particles. As defined by Gulliver (1899, pp. 76-77), wave base determines the ultimate depth of a platform of marine abrasion. No particular depth was specified, but in recent years several workers have placed its effective depth at about 10 meters, perhaps ulti- mately about twice this (Dietz and Menard, 1951; Fairbridge, 1952; Bradley, 1958). It is observed 00 that unconsolidated clay-size particles may be oj stirred up by heavy swell down to nearly 200 ^ meters, and this is ultimate wave base, but in no sense is this vigorous abrasion. Marine abrasion of consolidated rock is largely £ conditioned by the pre-rotting or loosening of the u coastal rocks by the subaerial chemical weathering S action of ground water (Bartrum, 1926). The role .0 of waves is thus primarily a mechanical one, to *J remove the debris (Fig. 1). Additional marine . erosional forces are (a) mechanical abrasion, sand * and boulders being propelled by wave action at the Ptf cliff foot, (b) hydraulic action (air compression in g" joints, etc.), and (c) biologic agencies (borers,'algal 3 buoyancy, etc.). g The principal locus of attack by all the above % agencies is the intertidal belt. In exposed areas § offshore, strong abrasion extends to the depth g where waves begin to peak and, under storm con- ° ditions, break. More tfian 95% of wave energy is o dissipated in this zone between about 10 meters and H EJ Initial. .2 ""ii:':.ilry 09 â g Fig. 1. The site of marine abrasion, involving the Jj removal of subaerially rotted rock waste as visualized by ^ Bartrum (1926). Wave action easily removes the "initial j§ zone of weathered rock" to the point A, producing a ^ cl
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