If measured from the ocean floor, its height of 7,500 m (24,600 ft) makes Teide the third-highest volcano in the world,[8] UNESCO and NASA rank it as Earth's third-tallest volcanic structure.

Teide's base is situated in Las Cañadas crater (the remains of an older, eroded, extinct volcano) at a height of around 2,190 m (7,190 ft) above sea level.

Teide is an active volcano: its most recent eruption occurred in late 1909 from the El Chinyero vent on the northwestern Santiago rift.

The volcano and its surroundings make up Teide National Park, which has an area of 18,900 hectares (47,000 acres) and was named a World Heritage Site by UNESCO in 2007.

[19] The same was true for the ancient Greeks and Romans, who believed that Vulcano and Mount Etna were chimneys of the foundry of the fire god Hephaestus (Vulcan in Latin).

It rests on the Las Cañadas caldera, an asymmetric depression 15 km (9.3 mi) in diameter in the form of a horseshoe which opens to the north.

This leads to a more continental climate on Teide, with strong changes in temperature over the course of the day (typically on the order of 15 °C) and in the course of the year (with a range of -15 °C in winter to 30 °C in the summer).

These winds carry moisture across the Atlantic and deliver rain to the north of Tenerife, forming in particular a dense layer of clouds between 800 and 1,600 ft (240 and 490 m) of altitude.

One hypothesis which allows reconciliation of these observations is the presence in the Earth's mantle of a convection cell which enters one part of the magma more towards the east, thus activating the old islands.

The lavas are basalts,[28] basic rocks (i.e. having a low content of silica) and therefore very fluid, this explains the characteristic form of shield volcanoes.

It was also in this period that the volcanic activity began in the rifts of the island, formed by radial fractures due to the thrust of magma in the central volcano.

Around 200,000 years ago, the peak of the volcano was swept away in a giant land slide to the north, forming the caldera of Las Cañadas.

The shield volcanoes date back to the Miocene and early Pliocene[31] and are preserved in three isolated and deeply eroded massifs: Anaga (to the northeast), Teno (to the northwest) and Roque del Conde (to the south).

[34] After this period of quiescence, the volcanic activity became concentrated within two large edifices: the central volcano of Las Cañadas, and the Anaga massif.

[33][44] From around 160,000 years ago until the present day, the stratovolcanoes of Teide and Pico Viejo formed within the Las Cañadas caldera.

Christopher Columbus reported seeing "a great fire in the Orotava Valley" as he sailed past Tenerife on his first voyage to the New World in 1492.

[citation needed] The summit of the volcano has a number of small active fumaroles emitting sulfur dioxide and other gases, including low levels of hydrogen sulfide.

[47] The authors further commented that "the recent eruptive record, combined with the available petrological and radiometric data, provides a rather optimistic outlook on major volcanic hazards related to Teide and its rift zones, posing only very localized threats to the one million inhabitants of Tenerife and the 4.5 million annual visitors to Teide National Park."

[50] In 1715 the English traveler J. Edens and his party made the ascent and reported their observations in the journal of the Royal Society in London.

[51][52] The German naturalist Alexander von Humboldt stopped in Tenerife during his voyage to South America in June 1799 and climbed Teide with his travelling companion Aimé Bonpland and some local guides.

[53] During an expedition to Kilimanjaro, the German adventurer Hans Heinrich Joseph Meyer visited Teide in 1894 to observe ice conditions on the volcano.

[51] More recently in November 2017, Gema Hassen-Bey became the first Paralympic athlete in the world in a wheelchair to reach 3,000 meters altitude with only the momentum of her arms.

[54] The lava flows on the flanks of Teide weather to a very thin but nutrient- and mineral-rich soil that supports a wide variety of plant species.

[59] These plants are adapted to the tough environmental conditions on the volcano, such as high altitude, intense sunlight, extreme temperature variations, and lack of moisture.

Adaptations include hemispherical forms, a downy or waxy cover, a reduction of the exposed leaf area, and high flower production.

Other mammals, such as the mouflon, the rabbit, the house mouse, the black rat, the feral cat, and the North African hedgehog, have all been introduced to the park.

Teide National Park is a useful volcanic reference point for studies related to Mars because of the similarities in their environmental conditions and geological formations.

[73] In 2010 a research team tested the Raman instrument at Las Cañadas del Teide in anticipation of its use in the 2016–2018 ESA-NASA ExoMars expedition.

This can cause people (especially with heart or lung conditions) to become light-headed or dizzy, to develop altitude sickness,[76] and in extreme cases to lose consciousness.

Teide has been depicted frequently throughout history, from the earliest engravings made by European conquerors to typical Canarian craft objects, on the back of the 1000-peseta banknote, in oil paintings and on postcards.