574 NOAH FIELDS DRAKE 
islands off the coast of southern California have their longer 
axes lying in the same direction as the opposite shore line and 
mountain range, showing that these islands belong to the sys- 
tem of orogenic movements that created the mountain ranges of 
the mainland and are remnants of partly submerged mountain 
ranges. 
The parallel grouping of mountain chains, which is so prom- 
inent a feature of the Coast Ranges to the north, is much less 
marked in the Sierra Madre Mountains, where the mountain sys- 
tem consists essentially of successive single ranges, somewhat 
elongated in the axial direction, but consisting of a central mass, 
from which spurs radiate in all directions. 
Owens River—Death Valley district.—This topographic region 
is the southern end of the Great Basin mountain system. The 
mountains and valleys of this system are parallel and run north 
and south. The mountains are usually high, and the valleys low 
and narrow. This topography is one of block faulting, which 
gives the great extremes in elevation and the narrow straight 
lines of mountain ranges and valleys. Drainage is now poorly 
defined, because the rainfall is so light that no permanent streams 
of any considerable length exist. Nearly every valley is a closed 
basin that has been filled to a considerable depth with detritus 
from the adjoining mountains. Death Valley, though having 
this usual filling of detritus, is, at its lowest place, 480 feet* 
below sea level. 
Mohave—Colorado River district—Southeastern California has 
rather low, irregular-shaped mountains, flat table-lands, and low, 
closed drainage basins. Nearly all the mountains and hills have 
the appearance of being partially buried, so that only their tops 
project, island-like, above the surrounding plains. In this region 
there is but little or no drainage to carry off the disintegrated 
rocks. The débris, blown and drifted around, fills the valleys 
until only the tops of the hills project above the débris-covered 
plain. This area is a meeting point for several mountain sys- 
tems, and therefore has a mixed arrangement of its mountains. 
*North American Fauna, No. 7, Death Valley Expedition, Part II, p. 367. 
