44 OS GAT VEL ee SLY 
stages of readvance during the general recession of the gla- 
cier), but are quite insignificant as compared with the lateral 
moraines. 
Near the heads of the glaciated valleys the rock surface is 
often bare over thousands of square feet, and is then seen to be 
smoothed and rounded by the grinding action of the ice. Some 
distinct grooves appear, but are not common. Of more frequent 
occurrence are fine lines or striz, altho where long exposed 
these have been destroyed by weathering. 
By far the most characteristic of the glacial phenomena of 
the Sierra Costa Mountains are the high meadows and lakelets. 
The former are smooth expanses of the valley floor a mile or 
more in length by half as great width, occurring near the heads 
- of the valleys. They are inclined to be damp and boggy, and 
are grassed, instead of timbered and brushy, as other portions of 
the mountain region. They are underlaid with a fine gravelly 
silty ground moraine, and over their surfaces are frequently 
scattered large erratics of an englacial and superglacial mode of 
transportation. The lakelets are rounded bodies of clear cold 
water, varying from a fraction of an acre to twenty or more 
acres in extent, sometimes occupying rock-bound basins of gla- 
cial origin, but generally held in behind moraines. Around the 
border may be a tiny beach of white sand, or a narrow strip of 
flat, grassy land composed of black peaty soil. Some of these 
tiny mountain tarns are perched high up on the mountain sides 
in small coves or niches abraded from the solid rock by the 
downward pressure of the ice under the névés. A few of these 
coves are hundreds of feet in depth, have steep, often precipi- 
tous, rock-walls, and are nearly closed in by the surrounding 
ridges so that they closely resemble the cevques of the Alps. 
An especially favorable situation for the glacial lakelets is at 
the foot of high rock precipices which usually occur onthe southern 
or western sides of the valleys. The glaciers invariably hugged 
the shady side of the valleys and there accomplished their most 
active grinding work. It was on the northern side of the frown- 
ing peaks that the ice laid longest, and when its final melting 
