The broad, flat plains of Rice Valley and the northwestern tip of the steep and rugged Big Maria Mountains lie within the borders of this wilderness. A system of small dunes rising 30 to 40 feet above the surface form a long, narrow band running through the middle of the valley floor. The valley is part of a massive Erg-sand sheet which extends from Cadiz Valley through Ward Valley, representing a part of one of the largest dune systems in the Desert Region of California. The Big Maria Mountains rise above the valley to an elevation of 2,000 feet.