Llullaillaco is a stratovolcano

Stratovolcano

A stratovolcano, also known as a composite volcano, is a tall, conical volcano built up by many layers of hardened lava, tephra, pumice, and volcanic ash. Unlike shield volcanoes, stratovolcanoes are characterized by a steep profile and periodic, explosive eruptions...

 at the border of Argentina

Argentina

Argentina , officially the Argentine Republic , is the second largest country in South America by land area, after Brazil. It is constituted as a federation of 23 provinces and an autonomous city, Buenos Aires...

 (Salta Province

Salta Province

Salta is a province of Argentina, located in the northwest of the country. Neighboring provinces are from the east clockwise Formosa, Chaco, Santiago del Estero, Tucumán and Catamarca. It also surrounds Jujuy...

) and 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...

. It lies in the Puna de Atacama

Puna de Atacama

The Puna de Atacama or Atacama Plateau is an arid high plateau averaging about above sea level and spanning an area of , in the Andes of northern Chile and Argentina and southwest Bolivia. Before the War of the Pacific , the region belonged to Bolivia. In 1898 it was ceded to Argentina in...

, a region of very high volcanic peaks on a high plateau within the Atacama Desert

Atacama Desert

The Atacama Desert is a plateau in South America, covering a strip of land on the Pacific coast, west of the Andes mountains. It is, according to NASA, National Geographic and many other publications, the driest desert in the world...

, one of the driest places in the world. It is the fifth highest volcano in the world, and it is also the seventh highest mountain of the Western Hemisphere

Western Hemisphere

The Western Hemisphere or western hemisphere is mainly used as a geographical term for the half of the Earth that lies west of the Prime Meridian and east of the Antimeridian , the other half being called the Eastern Hemisphere.In this sense, the western hemisphere consists of the western portions...

.

Llullaillaco follows the typical Puna de Atacama volcano pattern: it is surrounded by large debris fields, and is perpetually capped by snow and small glaciers despite the extremely dry conditions of the region.

The peak's name comes from Aymara

Aymara language

Aymara is an Aymaran language spoken by the Aymara people of the Andes. It is one of only a handful of Native American languages with over three million speakers. Aymara, along with Quechua and Spanish, is an official language of Peru and Bolivia...

 "murky water": llulla= dirty and yacu= water.