The caldera is , c. or wide and deep, and is one of the best preserved circular structures of the southern Central Andes, as well as one of its largest. It has also been interpreted as being actually three nested calderas. The Lomas de Montes lie along the northwestern and the Somma de Lars along the southeastern caldera margin. The caldera is filled with sediments as well as a 4.4-4.0 million year old ignimbrite that probably originated in the Laguna Amarga caldera.