treasure galleons returning from Manila to 

 Acapulco in 1565, 1605, 1606, and 1696 

 (Wagner, 1937) and stories of three ship- 

 wrecks in 1598, 1701, and 1754 (Coffman, 

 1957), the only known visitor to southern 

 California between 1543 and 1769 appears 

 to have been Sebastian Vizcaino. Sent out 

 from Acapulco to find refuge harbors for 

 the galleons after their experiences with 

 Francis Drake in 1578-1579 and with 

 Thomas Cavendish in 1587-1588, Vizcaino 

 spent about two weeks during November 

 1602 in the region, repairing his ships at 

 San Diego and visiting Santa Catalina Island 

 (Bolton, 1916). Although he described the 

 ports of San Diego and Monterey, settle- 

 ments were deemed unnecessary, at least for 

 the time being, because the gaUeons generally 

 stood far out from shore at these latitudes 

 and were running with scurvy-ridden crews 

 downwind as fast as possible on the last 

 part of the voyage to Acapulco. Vizcaino, 

 a merchant, made only a minor contribu- 

 tion to the knowledge of the coast and is 

 chiefly distinguished for having changed 

 the names of landmarks given by Cabrillo. 



In 1769 a permanent settlement, a presidio, 

 was estabUshed at San Diego by Caspar de 

 Portola in an effort by the Spanish to off'set 

 the advances of Russians from Alaska, 

 French from Canada, Dutch from the Cape 

 of Good Hope, and British from Cape Horn. 

 The two ships sent by Portola completed the 

 early exploration of southern California 

 coasts and the accumulated findings are re- 

 produced in a map of 1771. This map is 

 accurate in detail, and it also corrected the 

 errors of latitude and longitude that gave 

 rise to the westerly coastal trend shown by 

 earlier maps. To fix the hold of the Span- 

 iards on California, other presidios were 

 established at Monterey in 1770, San Fran- 

 cisco in 1776, and Santa Barbara in 1782, 

 and El Pueblo de Nuestra Senora la Reina 

 de Los Angeles de Porciuncula was founded 

 in 1781. During the overland trip to estab- 

 lish Monterey Fray Crespi noted topographic 

 details so carefully (Bolton, 1927) that, by 

 using his diary as a guidebook, we can very 

 closely follow his path from San Diego. 



One of the first visitors to the newly 



Physiography 



founded towns was Captain George Van- 

 couver who came during November 1793 to 

 investigate the status of occupation of the 

 region by the Spaniards. His is the first 

 known oceanographic work — the failure to 

 find bottom with several hundred fathoms 

 of line just off the Palos Verdes Hills (Wil- 

 bur, 1954). 



During the period of exploration and 

 settlement little was learned of the sea floor 

 until after California became a state in 1850. 

 Beginning in 1851 lead-line soundings were 

 taken by the U. S. Coast and Geodetic Sur- 

 vey in shallow waters of important bays, 

 and a few soundings were made in deeper 

 waters. In 1922 about 5000 weU-distributed 

 sonic soundings were made by the destroyers 

 U. S. S. Hull and Corry off southern California 

 and northern Mexico. Contours based on 

 these soundings revealed a complex topog- 

 raphy but left much to be desired, owing to 

 poor position control. New and improved 

 sonic surveys were made between 1935 and 

 1937 by the Coast and Geodetic Survey 

 with positions obtained by a radioacoustic- 

 ranging method. These brought the total 

 number of good soundings in the area to 

 about 500,000, of which nearly 300,000 are 

 deeper than 300 feet, an average density of 

 about 10 per square mile in deep water. On 

 the basis of these soundings the 300-foot in- 

 terval contours of Chart I were drawn by 

 Shepard and Emery (1941). Very similar 

 contours were drawn on U. S. Coast and 

 Geodetic Survey Charts 5101 and 5202, 

 which cover part of the same area. Since 

 1940 no general resurveys have been made, 

 and the modifications discovered through 

 local surveys which used recording echo 

 sounders and radar have been so minor as 

 to require no changes in the original contours. 



General Description 



The sea floor between the mainland shore- 

 line and the continental slope off" southern 

 California is much more complex than typ- 

 ical continental shelves of most other areas 

 of the world. For this reason it was named 

 the continental borderland by Shepard and 



