Perris Block

The Perris Block is the central block of three major fault-bounded blocks of the northern part of the Peninsular Ranges. The Perris Block lies between the Santa Ana Block to the west and the San Jacinto Block to the east. The Perris Block, was named by Walter A. English in 1925 for the city of Perris, located near the center of the block.

Structurally stable for millions of years, the Perris Block is an internally unfaulted, eroded mass of Cretaceous and older granitic rocks of the Southern California Batholith and metasedimentary basement rocks. These rocks compose various ranges of mountains and hills and monadnocks and underlie the valleys within it. It is bounded on the west by the Elsinore Trough, on the east and northeast by the San Jacinto Fault Zone including the San Jacinto Valley graben. It is bounded on the north by the Cucamonga Fault Zone, in the San Bernardino Valley and San Jose Hills Fault in the Pomona Valley. To the south, the Perris Block is bounded by the San Felipe Fault Zone between it and the Temecula, Aguanga, and Anza sedimentary basins that lie between Temecula and Anza. The interior of the Perris Block has various low bedrock mountains, hills and bedrock plains with intervening sediment-filled valleys, that make up six erosional surfaces sculpted by the effects of the vertical oscillation of the block during the Plio - era.