Part of the Austral Volcanic Zone of the Andes, its summit rises 1,000 metres (3,300 ft) above sea level and is capped by a crater about 1 kilometre (0.62 mi) wide.

A large eruption – among the largest known in the Austral Volcanic Zone – occurred 15,260–14,373 years before present and released over 5 cubic kilometres (1.2 cu mi) of tephra.

[5] Reclus is a 1,000 metres (3,300 ft) high pyroclastic cone, featuring a c. 1 kilometre (0.62 mi) wide summit crater[2] and is a small volcano.

[6] Seen from above, the volcano has the shape of an egg; the pointy end points due west and consists of 150–200 metres (490–660 ft) thick remnants of dacitic rocks of pre- or inter-glacial age.

The rest of the volcano consists of a 2,000 metres (6,600 ft) wide outcrop of violet-reddish-brown pyroclastic material that is in part covered by snow.

[7] In 2019, a 0.26 cubic kilometres (0.062 cu mi) landslide took place on its northeastern flank, which propagated below the Amalia Glacier.

[9] The Southern Patagonian Ice Field and the Cordillera Sarmiento are found in the neighbourhood of Reclus,[10] and Torres del Paine is c. 30 kilometres (19 mi) east of the volcano.

These rocks in the case of the Austral Volcanic Zone are all of adakitic character,[15] but there does not appear to be an unifying reason for this chemistry among the various volcanoes.

[17] Reclus together with Aguilera, Hudson and Monte Burney has been a major source of tephra for the region of Tierra del Fuego and Patagonia.

[28] The R1 tephra, originally identified in Patagonia as "Tephra A",[29] was deposited at various sites in southernmost Chile and Argentina such as Bahía Inutil,[22] Brunswick Peninsula,[30] Cardiel Lake,[31] Dawson Island,[32] East Falkland,[27] Estrecho de Magellanes,[22] Fitzroy Channel,[33] Muñoz Gamero Peninsula,[30] Laguna Potrok Aike,[34][c] Puerto del Hambre,[32] Río Rubens in Patagonia,[35] Seno Otway, Seno Skyring,[33] Tierra del Fuego[36] and in the Última Esperanza Province.

Ash fell as far as the Estrecho de Magallanes,[42] including the area of Bahia Inutil,[43] Dawson Island[44] and Punta Arenas.

[45] A set of tephras discovered at Torres del Paine,[46] Nordenskjöld Lake and other locations in Patagonia and emplaced between 8,270 ± 90 and 9,435 ± 40 radiocarbon years ago may have originated in minor eruptions of Reclus.

However, there is little evidence for large eruptions at Reclus during the late Holocene and the Puyehue-Cordón Caulle volcano in the Southern Volcanic Zone has been proposed as a source for this tephra.

[60] Possible eruption phenomena were reported in 2008 in form of tephra deposition and cracks in the glaciers,[61] and a landslide occurred on its northern side in 2017.