Page:Popular Science Monthly Volume 69.djvu/309

Rh clear. It may be that this is part of the Pájaro cross-fault. The original Portolá-Tomales fault, if continued in a straight line from Chittenden, would pass along the flanks or the foot of the Gavilan mountains to Priest Valley, fifty miles to the south-southeast. Beyond Priest Valley is a well-marked earthquake crack, which opened in the earthquake of 1868, and in earlier times. This extends through desert land in the same direction, its course being the axis of the Cholame Valley and the uninhabited desert sink known as Carisa Plain. This old rift extends at least one hundred and forty miles beyond Chittenden to Monte Pinos in the north edge of Ventura County. This whole fault from Point Arena to Monte Pinos is clearly a single break, but only 192 miles of a possible 330 were opened in the earthquake of 1906.

But while the surface break seemed to end at Chittenden, it seems probable that the rift in the rocks below extended much farther. At Priest Valley, fifty miles along this line, the shock was violent, while at localities ten miles or more to the east and west of the line, as at Lone Oak or the Pinnacles, it was very little felt. In Priest Valley chimneys and shelving were thrown down, buildings badly shaken and the contents of a country store impartially scattered over the floor, the shock being apparently about as severe as in San Francisco.

With the opening of the great rift it is conceivable that faults in the neighborhood should also be affected. There is evidence (most of which the writer has not examined) of the opening of a parallel fault behind Cape Mendocino. This seems to have passed across the base of the cape, cutting across the smaller headland called Point Delgada, losing itself in the Sonoma Valley to the southwest of Santa Rosa. There are distinct traces of it across Burbank's famous orchard at Sebastopol. Here on a slope lines of fruit trees were shifted, a well was moved bodily three or four feet, and a crack about one fourth mile long extended across a neighboring field, its direction parallel with that of the Tomales rift. Other similar cracks open at intervals on the road toward Point Delgada. The extreme violence of the shock in Santa Rosa perhaps indicates its nearness to this second rift, as the Tomales rift caused little damage in other towns equally far away. Dr. G. K. Gilbert takes a somewhat different view of this case. He seems to regard this Point Delgada crack as part of the great Tomales-Portolá rift. In his map ( August) Dr. Gilbert marks the great rift as swinging eastward in a curve across Point Delgada and to the eastward of Cape Mendocino between that headland and Humboldt Bay. It seems to the present writer far more probable that the Point Delgada fault is a separate rift, parallel with the main rift, and similar to it, except that it is a little less violent. There is some evidence that a fault line at the foot of San Francisco