MINOR GEOLOGICAL EFFECTS OF THE EARTHQUAKE. 403 
etc.; (2) the cracks and fissures which traverse the more firmly compacted forms of the 
same rocks, or others, such as granite, lava, etc., which occur only in a solid or coherent 
condition; (3) the vesicular spaces and tunnels of lavas, and (4) the spaces of dissolution 
which occur frequently in relatively soluble rocks, notably limestone. The occurrence 
of water which does not permeate the rocks nor flow thru them, but is contained in 
small discrete cavities in rocks, such as the liquid inclusions in igneous rocks and in the 
constituent minerals of sedimentary rocks, is here ignored. Thruout the Coast 
Ranges of California, limestones are not abundant and spaces of dissolution are believed 
to have played no part in the changes which were manifested in the behavior of springs 
and wells. The same remark holds with reference to vesicular and tunneled lavas. 
These changes were thus confined to the voids of porous and usually little coherent rocks 
and to cracks and fissures which traversed the coherent rocks, whether porous or not. 
In the discussion of certain earth-flows in the preceding section of this report, the 
initiation of which is ascribed to a sudden accession of water from the underlying for- 
mations, attention has been already directed to an extreme phase of the disturbance of 
the normal conditions of the ground-water. In those cases the ground-water was sud- 
denly expelled or squeezed out of saturated, incoherent formations at the time of the 
shock. They are extreme manifestations of a tendency which affected the ground 
water generally thruout the disturbed region. In this connection, it may be well 
to direct attention more particularly than has hitherto been done to the behavior of 
water contained in the alluvium of the river-bottoms. One of the most common phe- 
nomena in such situations was the expulsion of water in jets from apertures which sud- 
denly appeared in the flat-lying ground. The water was usually thrown into the air for 
several feet; in some cases it was reported to be as much as 20 feet, and the ejection 
continued for several minutes after the earthquake. The continuance of the ejection 
after the shock indicates that an elastic stress had been generated in the saturated ground, 
which thus found relief in the expulsion of the contained water or that there was a 
gravitational settling together of the material, which diminished the spaces occupied 
by water. The vents thus established were very numerous, and were in many instances 
closely spaced; more frequently a few to the acre, and occasionally isolated. These 
vents were easily recognizable for weeks and even months after the earthquake, in the 
form of craterlets. The water in its passage to the surface brought up considerable 
quantities of fine sand, which, from its prevailingly light bluish-gray color, was evi- 
dently derived from considerable depth. On the flood plain of the Salinas River, the 
sand was recognized by the people of the neighborhood to be the same as that of a 
stratum of sand pierced by wells at a depth of 80 feet. The craters were usually dis- 
tinctly funnel-shaped and were rimmed by a circular flat ridge of sand which, by 
reason of its light color, was in marked contrast to the surrounding surface. They 
varied in diameter from 1 to perhaps 10 feet. In some instances the funnels were 
several feet deep; in others the feeble action in the closing stages of the eruption had 
caused them to fill up with sand. They were quite analogous to the craterlets described 
and pictured in Dutton’s account of the Charleston earthquake.' (See plates 142, 8 
and 143a, B.) 
These craterlets occurred on practically all the saturated alluvial bottoms of the 
streams within the zone of destructive effects, and also on the tidal mud flats of Tomales 
Bay. They are significant of the compression to which such water-laden, incoherent 
formations were subjected by the passage of the earth-waves at the time of the earth- 
quake or by the consequent settling of the ground. They thus afford us, in part at 
least, a key to the behavior of many springs and wells. Most of the springs of the 
Coast Ranges are in solid rock, though they may emerge on a hillside mantled with rego- 

+ U.S. Geological Survey, 9th Ann. Report, pp. 296-298. 
