The light browns and tans of this photograph provide a clue to the natural environment for this part of southern California. This section of the Sonoran Desert shows two large, irrigated, cultivated field patterns where a variety of crops is grown—cotton, winter vegetables, alfalfa, citrus fruits, and dates. The Imperial Valley to the north contains large, regimented fields where mechanized, commercial agriculture is practiced (U.S. side of the border). The roughly triangular Colorado River delta shows smaller irrigated fields that are not neatly aligned (Mexican side of the border). The dark east-west line is the U.S.-Mexico border. A line of northwest-southeast-trending sand dunes, the Sand Hills, separates the Imperial Valley from the Chocolate Mountains to the east. The Salton Sea, 230 feet (70 meters) below sea level, is visible to the northwest. The highly reflective Laguna Salada, extending south of the border, intermittently receives water.