It is located southwest of the Nevados de Quimsachata volcanic group; some sources classify Guallatiri as a member.

The term Guallatiri is derived from wallatiri, which means 'abundance of the Andean goose' in Aymara,[2][3] referring to the birds' frequent occurrence in the area.

[8] The volcano is considered to be easy to ascend (rated F on the French Climb grading by John Biggar) but toxic gases constitute a hazard in the summit region.

[20] The frontier between Bolivia and Chile runs along the Nevados de Quimsachata northeast of Guallatiri,[21][1] not far from the volcano.

[32] Thick lava flows emanate in all directions[15] but are primarily noted on the northern and western flanks.

[34] The lava flows have a lobate appearance even when they are heavily eroded, and display levees, ogives, polygonal cracks and blocky surfaces.

[37] Apart from volcanic rocks, glacial deposits cover large parts of the volcano,[38] and there are traces of mass failures.

[43] One hot spring is located at Chiriguaya on the northwestern foot of Guallatiri,[38] where temperatures of 48 °C (118 °F) were measured in bubbling pools,[44] and sinter deposition takes place.

[51] Some glaciers were still present during the Holocene, evidenced by Holocene-age Domo Tinto lava dome which bears traces of glacial erosion[41] and is partially covered by moraines.

[53] The CVZ is a 1,500 km (930 mi) long chain of volcanoes[54] spanning southern Peru, northern Chile, western Bolivia and northwestern Argentina.

The most active CVZ volcano is Lascar, which in 1993 produced the largest historical eruption of northern Chile.

[55] Guallatiri rises above Oligocene to Pliocene age volcanic and sedimentary rocks, which define the Lupica and Lauca Formations.

[38] The rocks define a potassium-rich calc-alkaline suite and contain amphibole, apatite, biotite, clinopyroxene, olivine and plagioclase phenocrysts, similar to other volcanoes in the region.

[59] Fumaroles have deposited minerals such as anhydrite, baryte, cristobalite, gypsum, quartz, sassolite and sulfur.

[60] Sulfur deposits have yellow, orange or red colours and are sometimes accompanied by arsenic-sulfur compounds[61] that also contain iodine, mercury, selenium and tellurium.

[64] The volcano is inside the Lauca National Park[65] and the wetlands (Spanish: Bofedales) in the area of Guallatiri have regional importance.

[66] Vegetation there include Arenaria rivularis, Calandrinia compacta, Deyeuxia curvula, Distichlis humilis, Lobelia oligophylla and Oxychloe andina.

[71] Volcanic activity at Guallatiri commenced either about 710,000[30] or 262,000–130,000 years ago[39] and the volcano subsequently grew during the Pleistocene[g] and Holocene.

Initially, the "Guallatiri I" stage grew in the form of andesitic and dacitic lava flows as well as heavily eroded pyroclastic deposits, which crop out around the volcano.

[39] The central sector of the volcano is mainly of Holocene age while the peripheral parts date to the Pleistocene.

[38] In 2021, Sepúlveda et al. envisaged six[i] separate stages,[73] rocks from the first four crop out mainly at the periphery of the volcano and the last two in its central sector.

[40] They form when volcanic material interacts with water, produced either by the melting of ice or through intense rainfall.

[83] Increased steam emission was observed in December 1985 and initially attributed to Acotango volcano, before it was linked to Guallatiri;[84] it may have been an eruption of the latter.

[43] Different degrees of interaction with precipitation water may explain why the south-southwestern flank fumarole gases have a different composition than these released in the summit region.

[91] The fumarolic activity has produced intense hydrothermal alteration of Guallatiri's rocks[39] east-northeast of the summit and at a lower elevation northwest of it.

[93] Puffing behaviour was noted in 1996[85] and emissions every half-hour in November 1987, which gave rise to yellow-white plumes up to 1 km (0.62 mi) high.

[30] Lahars would mainly impact the western and southwestern sectors of the volcano, as the snow cover is concentrated there.

In 2013, the Southern Andean Volcano Observatory began to monitor Guallatiri by video, measurements of seismic activity and deformations of the volcanic structure.

[98][2] The mountain was and still is worshipped by local inhabitants, and the church in the town of Guallatiri is constructed so that it points to the volcano.

[3] In the oral tradition of Chipaya, cold winds called soqo blow from the Pacific Ocean to the Altiplano and towards Guallatiri.