PHYSICAL SETTING OF CHILEAN BORATE DEPOSITS 765 
slopes of the volcanic cones rise directly from the shores of the 
borate lake. In the so-called lake very little water is seen; most 
of its surface is a white field of borate which rests upon the watery 
mass below like ice upon a partially frozen pond. It is really a 
borate incrusted lake bed. 
The craters of the adjoining volcanoes are all quite recent, 
and some of them are probably dormant rather than extinct. 
Ollagiie at least still emits a thin thread of smoke from an orifice 
in its upper slopes. Drainage lines are not yet well established, 
Fic. 1.—Volcano on border of Ascotan Borax Lake. The drainage from the 
crater passes directly into the lake. 
but whatever drainage and seepage there may be from these 
cinder cones would necessarily pass, in large part, directly into this 
lake basin. Underground drainage from several large volcanoes 
would find its way into the borax lake. One of the craters was 
seen to have its wall broken down on the side toward the lake so 
that much of the surface runoff from the crater walls as well as 
the underground seepage through the cinder cone would go directly 
to the lake (Fig. 1). 
The lake has no apparent outlet so that the small amount of 
water on the lake bed represents a state of balance between the 
