Portal de Periódicos da CAPES

The Formation of the Lesser Antilles

1924; National Academy of Sciences; Volume: 10; Issue: 6 Linguagem: Inglês

10.1073/pnas.10.6.205

1091-6490

W. M. Davis,

Tropical and Extratropical Cyclones Research

The Islands.-The island chain of the Lesser Antilles extends in a curve about 500 miles in length between Porto Rico and Trinidad, and includes 25 larger members with an uncounted number of smaller ones. Most of the islands are of volcanic origin, now in various stages of dissection; but five of the larger islands and two small ones consist wholly of calcareous strata, and five others are composed of both volcanic rocks and calcareous strata. Vieques and St. Croix, southeast of Porto Rico, and Barbados, east of the southern part of the chain, are of other origins. The following inferences regarding the history of the islands are based on observations made during a voyage in October and November, 1923, and on a study of all available charts and published articles. A fuller statement is in preparation for publication elsewhere. The Circuminsular Banks.-Many of the islands are associated with submarine banks, from 20 to 40 or 50 fathoms in depth. The largest of these extends SO miles eastward from Porto Rico with a width of 25 or 30 miles, and bears the mountainous Virgin islands, five of which are from 3 to 11 miles in length; but not St. Croix, which rises from a much smaller bank of its own, farther south. The second largest bank is at the other end of the chain, next north of Trinidad; it has a length of 98 miles and a breadth of from 10 to 17 miles, and includes the mountainous island of Grenada as well as the little Grenadines. Other island-bearing banks will be mentioned below. Besides these, a few additional banks, mostly of moderate or small size, are charted without islands; the largest of these is Saba bank, 33 by 20 miles. Relation of Islands and Banks.-In general, the younger a volcanic island the smaller the bank around it; the older the island, as indicated by the stage of its dissection, the larger the associated bank. Thus Saba island, near the bank of the same name, is a young, moderately clift volcanic cone, 3 miles across and 2820 feet high, with a bank less than a mile