Mentolat is an ice-filled, 6 km (4 mi) wide caldera in the central portion of Magdalena Island, Aisén Province, Chilean Patagonia.

The earliest activity occurred during the Pleistocene, and Mentolat has had some major explosive eruptions during the Holocene.

The etymology of Mentolat has been tentatively linked to Men (o) lat, which in the Chono language means "to decipher".

[6] Mentolat lies on the central part of Isla Magdalena of southern Chile,[3] close to the town of Puerto Cisnes in the Aysen Region,[7] from which it is separated by the Puyuhuapi strait.

[9][12] Phenocrysts contained in Mentolat's rocks include: clinopyroxene, olivine, orthopyroxene and plagioclase.

This subduction occurs at an angle and has generated the Liquiñe-Ofqui fault zone which runs along the volcanic arc.

[22][26] Volcanic activity is absent in the 500 kilometres (310 mi) long area, as its subduction disrupts the slab.

[30] Until 17,800 years before present, the region southeast of Hudson was covered by the glaciers of the last ice age.

[32] The volcanic activity has been inferred from tephra layers in lakes and outcrops,[30] about 13 eruptions have been identified with the help of tephrochronology.

[7] Less than 6,960 years before present, a basaltic andesite-andesite ash of yellow ochre colour was erupted from Mentolat.

[17][18] Early in the 18th century, Mentolat erupted and formed lava flows on its western flank.

[35] No historical records of activity exist, however,[9] although reports by Serrano in the 18th century may refer to a lava flow from Mentolat.

[27] The largest Holocene volcanic eruption of the Southern Andes occurred 6,700 years before present at Cerro Hudson.

[37] Tephra layers found at Mallín El Embudo have been attributed to Mentolat, as well as to Melimoyu and Cerro Hudson.