History
The Preserve has a desert climate with hot, dry summers and moderate winters. Rainfall is scarce, with an annual average of 8 inches. The Morongo Fault, running through the canyon, causes water from melting snow on the surrounding San Bernardino Mountains to form Big Morongo Creek. The creek intermittently rises to the surface for just three miles, between the Mojave and Sonoran Deserts, before it disappears underground again.
The water percolates into the sandy soil as it crosses the Morongo Basin, but as it enters Big Morongo Canyon, it encounters "fault gouge" (pulverized rock), which forces it above ground, creating a unique desert wetland with a series of perennial springs.
The stream is a lifeline for bighorn sheep and mule deer and more than 240 species of migrating and breeding birds. Sunset reveals other wildlife, including raccoons, bobcats, and coyotes. A variety of reptiles are found here, including whip-tailed lizards, desert spiny lizards, and the common king snake. The Pacific tree frog also finds a home here, as do a wide variety of butterflies, dragonflies, and damselflies.
Big Morongo Canyon has some of the oldest exposed rocks in California, dated at almost two billion years. They consist of granite that has been altered by centuries of heat and pressure to form gneiss and schist.
