MCGEK] THE SURFACE OF TIBURON 43 



ant. Sierra Meiior is a third term in the mountain series, in structure 

 and geomorphy as in altitude; while the interior plain is a homologue 

 of that portion of Desierto Encinas lying north of Playa Noriega — 

 i. e., of its (potentially) free drained portion. Almost the entire perim- 

 eter of Tiburon is suttering marine transgression, and is faced with 

 seacliffs overlooking wave-carved shelves; and in both form and struc- 

 ture the greater part of the coast rei)eats, with minor variations, the 

 f<^atures of the mainland coast from Punta Ygnacio northward. Partly 

 because of the superior magnitude and height of its debris-yielding 

 sierra, partly because of protection from the wave-beat of the open 

 gulf, the eastern shore is skirted with a talus shape slope, usually two 

 to four miles wide; and while there are unmistakable evidences of 

 sheetHood carving in the higher portions of this plane, the coastal cliff 

 commonly reveals nothing but heterogeneous debris, sometimes rising 

 thirty or forty feet above tide. Somewhat the greater part of the vol- 

 ume of this debris is fine — i. e., sand and silt and nondescript rock- 

 matter; but there is. always a considerable element of larger rock- 

 fragments, which gather along the shore in a pavement of bowlders 

 and cobbles (upper figure of i)late v). These coarse materials — impor- 

 tant factors in aboriginal industry — are harmoniously distributed ; more 

 conspicuously on the ground than on the map, the coast is set with 

 salients (of which Punta jSTarragansett is a type), consisting merely of 

 exceptional accumulations of debris from gorges in the sierra and from 

 shallow arroyos, or pebble washes, traversing the coastwise plain. These 

 salients owe their prominence i)artly to the relative coarseness, ])artly 

 to the abundant supjdy, of fragmental material from the heights; and 

 about their extremities the beach is paved with bowlders, which grade 

 to cobbles or even to pebbles along the reentrant shores on either 

 hand. This distribution of cobbles is one of the conditions govern- 

 ing the placement of Seri rancherias ; and in many cases the jacales are 

 located, either singly or in groups, where the coastal salients and 

 reentrants meet, and where there is an abundant supply of cobbles of 

 convenient size and wave- tested hardness. 



The coastwise plain skirting eastern Tiburon has a few wave V)uilt 

 projections analogous to those east of El Infiernillo; the most con- 

 si)i(uaous of these are Punta Tormenta, Punta Tortuga, and Punta 

 Perla with its tide-swept extensions, Bajios de Ugarte. All of these 

 are located primarily by sierra-fed arroyos, but all are greatly extended 

 by wave-borne material laid down along lines determined by the pre- 

 vailing currents of this best-protected portion of the coast. The long- 

 outer face of Punta Tormenta, shaped by the storms of Bahia Kun- 

 kaak, is strikingly regular and symmetric; its broad extremity and 

 inner face are diversified by subordinate bars and lagoons, evidently 

 tending to connect with the main coast toward Punta Tortuga, and 

 thereby to transform the whole of Rada Ballena into a lagoon. 

 Already the narrow embayment is so shallow that, although a com- 



