Back to Homepage Caribbean History Caribbean until 1900 1900s Caribbean Caribbean Area Bahama Islands Jamaica, Cayman Islands, Turks and Caicos Islands, Morant and Pedro Cays Leeward Islands Windward Islands Barbados Trinidad and Tobago Guiana Honduras Martinique   Guadeloupe and Dependencies French Guiana Clipperton Island The Territory of Curaçao Surinam Economy The International Importance of the Banana Trade United States Trade with the Caribbean Oil on the Caribbean

Normal and Plunging Sea Cliffs A paragraph may be here introduced in order to give fuller warrant for the conclusion that the headland cliffs of St. Lucia, as well as of several other islands, were cut during a time of greater emergence than now, because the cliff faces plunge beneath present sea level. For certain islands the plunging of cliffs beneath sea level is inferred from the recorded soundings on large-scale charts with greater emergence than now, because the cliff faces plunge beneath present sea level. For certain islands the plunging of cliffs beneath sea level is inferred from the recorded soundings on large-scale charts with depths of five or ten fathoms near the shore; but for several headlands on St. Lucia, as well as on St. Thomas, later to be described, the plunge of the cliffs into blue water was directly observed as I passed them in launches. Such cliffed headlands have no beaches along their shore line, nor are they fronted by a shallow rock platform bearing ragged ledges or pointed stacks such as may often be seen near the base of cliffs that have been cut back at present sea level. Two normal sea cliffs may be instanced. First, the chalk cliffs of Normandy are manifestly the work of abrasion and are as manifestly retreating actively in consequence of the attack of the waves at their base. This is proved by the not infrequent cracks seen on the upland surface a little distance back from the cliff top and of so recent origin that they cross the lines of plow furrows; it is also shown by the not infrequent occurrence of recently fallen cliff-face slabs, which form rock-fall cones not yet removed by the waves. The rock platform at the cliff base is ordinarily covered by a sheet of detritus, chiefly composed of chalk flints, which forms a pebble beach along the shore and extends seaward below low-tide level with gradually increasing depth; but the platform is occasionally and locally laid bare near the shore, presumably by storm action, and it may then be seen to lie between low- and high-tide levels. A second instance may be cited from the southern end of the North Island of New Zealand, near Wellington, where the coast, which I saw in company with Mr. C. A. Cotton in 1914, was suddenly elevated a few feet at the time of an earthquake threequarters of a century ago. There the cliff-base platform is well revealed. It rises landward very gradually from the new shore line, bearing a few small unconsumed rock stacks and patches of gravel; its line of junction with the cliff base is a little lower than the gravel beaches which must have stood a little above high-tide level when the platform and cliff were in process of production. With these indications of the normal relation between cliffs, platforms, and sea level in mind, it seemed to me clear that the plunging cliffs of St. Lucia recorded a change in the relative attitude of land and sea. Their plunge might be explained as a consequence of insular subsidence in an ocean of constant level. In view, however, of the repeated occurrence of plunging-cliff islands in the marginal belt of the coral seas, where they are so constantly associated with rather extensive submarine banks and with imperfect bank reefs, the plunge of the cliffs seems best explained by the Postglacial rise of the ocean from the somewhat lowered level it had in the Glacial epochs, when it is supposed the cliffs were cut because of the temporary lapse of reef protection which the islands had long previously enjoyed.   Home