[1] There are four summits, all principally created by phreatomagmatic activity[8] and which conspicuously rise above the surrounding area and give the mountain its name.

[10] Melimoyu displays a large ice cap which after shrinkage over the preceding few decades covered a surface area of 55.59 square kilometres (21.46 sq mi)[13] through a retreat rate of about 0.61 square kilometres per year (0.0075 sq mi/Ms) between 1970-2017;[14] said shrinkage also led to the retreat of outlet glaciers and the development of a proglacial lake.

Aside from Melimoyu, the volcanoes Mentolat and Yanteles, the Puerto Bonito hot springs as well as local bays and estuaries are influenced by this fault system.

[19] Two large Holocene eruptions have been identified at Melimoyu, called MEL1 and MEL2[1] and whose deposits are known as the La Junta and Santa Ana tephras respectively.

[10] The larger MEL1 eruption occurred between 2,790 – 2,740 years ago and produced a layered basaltic-dacitic tephra consisting of pumice with lithics and scoria inclusions.

[6] A 6 centimetres (2.4 in) thick tephra deposit at Lago Shaman and Mallín El Embudo in the Río Cisnes valley has been attributed to the MEL2 eruption.

[9] Two additional tephra layers, 8,300 and especially one 19,700 years old, at Río Cisnes may also have originated at Melimoyu[10] and deposits from the latter eruption may also be preserved in the Ñirehuao valley.

[26] Local towns such as Puerto Cisnes may experience tephra falls in case of renewed volcanic activity at Melimoyu,[12] while lahars and lava bombs would threaten the area directly surrounding the volcano.