Sollipulli is an ice-filled volcanic caldera

Caldera

A caldera is a cauldron-like volcanic feature usually formed by the collapse of land following a volcanic eruption, such as the one at Yellowstone National Park in the US. They are sometimes confused with volcanic craters...

, which lies about 12 kilometres south of the small town of Melipeuco

Melipeuco

Melipeuco is a town and commune in Chile, located at the foot of the Andes, in the Province of Cautín, Araucanía Region. Melipeuco is from the southern entrance of the Conguillío National Park. The Nevados de Sollipulli, an ice-filled volcanic caldera surrounded by numerous hot water springs and...

 in the Araucanía Region

Araucanía Region

The IX Araucanía Region is one of Chile's 15 first order administrative divisions and comprises two provinces: Malleco in the north and Cautín in the south....

, Chile

Chile

Chile ,officially the Republic of Chile , is a country in South America occupying a long, narrow coastal strip between the Andes mountains to the east and the Pacific Ocean to the west. It borders Peru to the north, Bolivia to the northeast, Argentina to the east, and the Drake Passage in the far...

. Volcan Sollipulli lies northeast of Caburgua Lake

Caburgua Lake

Caburgua Lake is located 23 km northeast of the city of Pucón, in the Araucanía Region of Chile. Huerquehue National Park lies to the east of the lake. Like Villarrica Lake, it is part of Toltén River basin...

 and southeast of Llaima

Llaima

Llaima Volcano is one of the largest and most active volcanoes in Chile. It is situated 82 km northeast of Temuco and 663 km southeast of Santiago, within the borders of Conguillío National Park.-Geography:...

 volcano; and there are views to at least seven active volcanoes from the summit rim. The volcano has evolved in close contact with glacial ice

Glacier

A glacier is a large persistent body of ice that forms where the accumulation of snow exceeds its ablation over many years, often centuries. At least 0.1 km² in area and 50 m thick, but often much larger, a glacier slowly deforms and flows due to stresses induced by its weight...

 and has some typical subglacial volcanic

Subglacial volcano

A subglacial volcano, also known as a glaciovolcano, is a volcanic form produced by subglacial eruptions or eruptions beneath the surface of a glacier or ice sheet which is then melted into a lake by the rising lava...

 features such as hyaloclastite

Hyaloclastite

Hyaloclastite is a hydrated tuff-like breccia rich in black volcanic glass, formed during volcanic eruptions under water, under ice or where subaerial flows reach the sea or other bodies of water. It has the appearance of angular flat fragments sized between a millimeter to few centimeters...

 breccia

Breccia

Breccia is a rock composed of broken fragments of minerals or rock cemented together by a fine-grained matrix, that can be either similar to or different from the composition of the fragments....

 and pillow lava

Pillow lava

Pillow lavas are lavas that contain characteristic pillow-shaped structures that are attributed to the extrusion of the lava under water, or subaqueous extrusion. Pillow lavas in volcanic rock are characterized by thick sequences of discontinuous pillow-shaped masses, commonly up to one metre in...

. It differs from many calderas in that Sollipulli appears to have collapsed in a non-explosive manner. The age of collapse is not yet known, but since the caldera formed, volcanic activity has continued along the surrounding ring faults which have produced lava flows and lava dome

Lava dome

|250px|thumb|right|Image of the [[rhyolitic]] lava dome of [[Chaitén Volcano]] during its 2008–2009 eruption.In volcanology, a lava dome is a roughly circular mound-shaped protrusion resulting from the slow extrusion of viscous lava from a volcano...

s, increasing the elevation of the caldera wall. The caldera is 4 km in average diameter and according to ground penetrating radar measurements made in 1993 it contained a maximum ice thickness of at least 550 m, but perhaps as much as 650 m, at that time.