Joshua Tree encompasses three of California's ecoregions. Its geology shows the effects of plate tectonics, volcanism, mountain-building, and stark erosion. With elevations ranging from 900 feet to over 5000 feet above sea level, the park is home to a diversity of biological communities found nowhere else in such proximity. Sand dunes, dry lakes, flat valleys, extraordinarily rugged mountains, granitic monoliths, and oases are all found within its nearly 800,000 acres. Each feature makes its contribution to the natural tapestry of the southwest.