Ojos del Salado.

Nevado Ojos del Salado is a massive stratovolcano in the Andes on the Argentina–Chile border and the highest active volcano in the world at 6,893 m (22,615 ft). It is also the second highest mountain in the Western Hemisphere and Southern Hemisphere and the highest in Chile. It is located about 600 km (370 mi) north of Aconcagua, the highest mountain in the Western Hemisphere at 6,962 m (22,841 ft).

Due to its location near the Atacama Desert, the mountain has very dry conditions with snow usually only remaining on the peak during winter, though heavy storms can cover the surrounding area with a few feet of snow even in summer. Despite the generally dry conditions, there is a permanent crater lake about 100 m (330 ft) in diameter at an elevation of 6,390 m (20,960 ft) on the eastern side of the mountain. This is most likely the highest lake of any kind in the world.

Llullaillaco

Llullaillaco is a stratovolcano at the border of Argentina (Salta Province) and Chile. It lies in the Puna de Atacama, a region of very high volcanic peaks on a high plateau within the Atacama Desert, one of the driest places in the world. It is the second highest volcano in the world[citation needed], and it is also the seventh highest mountain of the Andes.

Llullaillaco follows the typical Puna de Atacama volcano pattern: it is surrounded by large debris fields and is perpetually capped by small snow patches, though there are no true glaciers due to the extreme aridity. The snow line in this region is the highest in the world, at around 6,500 metres (21,300 ft), which is around 1,000 metres (3,300 ft) higher than in the Himalayas and 2,000 metres (6,600 ft) higher than in the Andes of Colombia and Ecuador.

Chimborazo

Chimborazo is a currently inactive stratovolcano in the Cordillera Occidental range of the Andes. Its last known eruption is believed to have occurred around 550 AD.

With a peak elevation of 6,268 metres (20,564 ft), Chimborazo is the highest mountain in Ecuador. It is the highest peak near the equator. Chimborazo is not the highest mountain by elevation above sea level, but its location along the equatorial bulge makes its summit the farthest point on the Earth's surface from the Earth's center.

Elevation

With an elevation of 6,268 m, Chimborazo is the highest mountain in Ecuador and the Andes north of Peru; it is higher than any more northerly summit in the Americas.

Pico de Orizaba

The Pico de Orizaba, or Citlaltépetl (from Nahuatl citlal(in) = star, and tepētl = mountain), is a stratovolcano, the highest mountain in Mexico and the third highest in North America. It rises 5,636 metres (18,491 ft) above sea level in the eastern end of the Trans-Mexican Volcanic Belt, on the border between the states of Veracruz and Puebla. The volcano is currently dormant but not extinct with the last eruption taking place during the 19th century. It is the second most prominent volcanic peak in the world after Africa's Mount Kilimanjaro.

Nevado del Ruiz

The Nevado del Ruiz. also known as La Mesa de Herveo (English: Mesa of Herveo (the nearby town)), or Kumanday in the language of the local pre-Columbian indigenous people, is a volcano located on the border of the departments of Caldas and Tolima in Colombia, about 129 kilometers (80 mi) west of the capital city Bogotá. It is a stratovolcano, composed of many layers of lava alternating with hardened volcanic ash and other pyroclastic rocks. Nevado del Ruiz has been active for about two million years, since the early Pleistocene or late Pliocene epoch, with three major eruptive periods. The current volcanic cone formed during the present eruptive period, which began 150 thousand years ago.

The volcano usually generates Plinian eruptions, which produce swift-moving currents of hot gas and rock called pyroclastic flows. These eruptions often cause massive lahars (mud and debris flows), which pose a threat to human life and the environment. The impact of such an eruption is increased as the hot gas and lava melts the mountain's snowcap, adding large quantities of water to the flow. On November 13, 1985, a small eruption produced an enormous lahar that buried and destroyed the town of Armero in Tolima, causing an estimated 25,000 deaths. This event later became known as the Armero tragedy—the deadliest lahar in recorded history. Similar but less deadly incidents occurred in 1595 and 1845, consisting of a small explosive eruption followed by a large lahar.