Forest Falls is situated in the
San Bernardino Mountains of
California, at elevations ranging from approximately to along the steep gradient of Mill Creek, a tributary of the Santa Ana River. It lies due east of the Los Angeles Civic Center, and from San Bernardino, the nearest large city and the county seat. The community stretches for approximately 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 , 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. 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 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 per 1,000 years in Mill Creek Canyon on hillside gradients as high as 36 degrees.
Climate Forest Falls, in common with the rest of California, enjoys a
Mediterranean climate, receiving the majority of its precipitation during the winter months, frequently in the form of snow. Temperatures are temperate, reaching average highs in the 80s during the summer, and lows in the 20s during the winter. Precipitation is higher than in the adjacent valleys and averages more than per year. Summer thunderstorms occasionally occur, particularly in the later part of the season. The amount of snow received during winter months largely depends on the area of Forest Falls under consideration, as the community extends over an elevation range of approximately . Upper Canyon, as it is locally known, that is, the eastern higher-elevation end of the community, receives on average twice the amount of snow fall as Lower Canyon. Snowfall varies, but on occasion as much as six to seven feet has been recorded, the most on average however is around one to two feet sporadically throughout the winter. ==See also==