California's Colorado Desert is a part of the larger Sonoran Desert. It encompasses approximately , including the heavily irrigated Coachella and Imperial valleys. It is home to many unique flora and fauna. Geography and geology The Colorado Desert is a subdivision of the larger Sonoran Desert encompassing approximately . The desert encompasses Imperial County and includes parts of San Diego County, Riverside County, and a small part of San Bernardino County, California, United States. Most of the Colorado Desert lies at a relatively low elevation, below , with the lowest point of the desert floor at below sea level, at the Salton Sea. Although the highest peaks of the Peninsular Ranges reach elevations of nearly , most of the region's mountains do not exceed . In this region, the geology is dominated by the transition of the tectonic plate boundary from rift to fault. The southernmost strands of the San Andreas Fault connect to the northernmost extensions of the East Pacific Rise. Consequently, the region is subject to earthquakes, and the crust is being stretched, which will result in a sinking of the terrain over time. Climate The Colorado Desert's climate distinguishes it from other deserts. The region experiences greater summer daytime temperatures than higher-elevation deserts and almost never experiences frost. In addition, the Colorado Desert experiences two rainy seasons per year (in the winter and late summer), especially toward the southern portion of the region; the more northerly Mojave Desert usually has only winter rains. The west coast Peninsular Ranges, or other west ranges, of Southern California–northern Baja California, block most eastern Pacific coastal air and rains, producing an arid climate. Other short or longer-term weather events can move in from the Gulf of California to the south, and are often active in the summer monsoons. These include remnants of Pacific hurricanes, storms from the southern tropical jetstream, and the northern intertropical convergence zone. Flora and fauna The region's terrestrial habitats include creosote bush scrub; mixed scrub, including yucca and cholla cactus; desert saltbush; sandy soil grasslands; and desert dunes. Higher elevations are dominated by pinyon pine and California juniper, with areas of manzanita and Coulter pine. In addition to hardy perennials, more than half of the desert's plant species are herbaceous annuals, and appropriately timed winter rains produce abundant early spring wildflowers. In the southern portion of the region, the additional moisture supplied by summer rainfall fosters the