343 



and loosely consolidated sandstone and shale flanking the moun- 

 tain below (at the left). West of Tahquitz Lodge and the 

 junction of the highway that leads by Idyllwild over the moun- 

 tain range to Banning the highway winds along the valley of 

 San Jacinto River, which is eroded in the crushed and fractured 

 rocks of the fault zone. Hemet (67 miles from Palm Springs) 

 is on the broad alluvial plain of San Jacinto Valley. San 

 Jacinto (town) is three miles north. 



The Perris Plain 



The route west to Perris (14 miles) is across the eroded roll- 

 ing granite plain (described in Chap. XVIII) . From Perris the 

 highway north leads via March Field to Riverside (17 miles). 

 Turn left (southwest) at Perris, over the rolling granite- 

 knobbed plain to Elsinore (11 miles) . Lake Elsinore lies in the 

 valley which was formed by the sinking of the land east of the 

 fault that bounds the Santa Ana Mountains on the east. This 

 is known as the Elsinore fault. Temescal Canyon lies along the 

 foot of the fault scarp, which is the eastern steep rugged face 

 of the Santa Ana Range. The fault extends for 50 miles, and 

 joins the Whittier fault in the north. The Elsinore basin is the 

 result of a downward movement of the rock floor east of the 

 fault. 



Temescal Valley and Clay Deposits 



At Alberhill, seven miles north of Elsinore, are clay deposits 

 which form the basis of an important ceramic industry. 

 Glazed and unglazed tile and brick are manufactured on a large 

 scale. As much as 100,000 tons of clays of many distinct 

 varieties are used yearly. The clays come largely from three 

 different localities, though there are many pits occurring in an 

 area 30 miles long and two miles wide. The clays crop out in 

 irregular patches among sandstones and shales. They lie di- 

 rectly upon or close to the basement bed-rock of granite, and 

 are of early Tertiary age. 



