Forest Falls Welcome Center

er, and 21 miles (34 km) from San Bernardino, the nearest large city and the county seat. The community stretches for approximately 5 miles (8.0 km) in a narrow band primarily along the south side of the linear canyon of Mill Creek, which trends slightly north of east. The highest portions of the San Bernardino Mountains, including southern California's highest point, San Gorgonio Mountain at 11,503 feet (3,506 m), lie directly north of Forest Falls in the San Gorgonio Wilderness Area. The falls for which the community is named descend from this high area over the northern edge of the canyon of Mill Creek. Geology
The rocks immediately surrounding Forest Falls are basement rocks characteristic of the major part of the San Bernardino Mountains, that is, Paleoproterozoic gneiss, Neoproterozoic to Paleozoic marble and quartzite, and Late Cretaceous granitic rocks. Marble and quartzite are present only in minor amounts in the immediate vicinity, although a small marble quarry up-canyon from the town was operated sporadically and uneconomically from 1908 into the 1940s. The extremely linear canyon in which Forest Falls is located follows the trace of the Mill Creek Fault, a now-inactive strand of the San Andreas Fault system along which approximately 8 kilometres (5.0 mi) of right-lateral strike-slip displacement occurred during the period from 500,000 to 250,000 years ago. (Presently active strands of this fault system lie to the south.) The canyon itself is the result of erosion by Mill Creek of the highly fractured rock along this linear fault zone. Because the San Bernardino Mountains are a young, steep and rapidly rising mountain range, erosion rates are extremely high and have been estimated to average as great as 1,560 millimetres (61 in) per 1,000 years in Mill Creek Canyon on hillside gradients as high as 36 degrees.