<P> Two theories on the formation of the 16 km × 9 km (9.9 mi × 5.6 mi) caldera exist . The first states that the depression is the result of a vertical collapse of the volcano triggered by the emptying of shallow magma chambers at around sea level under the Las Cañadas volcano after large - volume explosive eruptions . The second theory is that the caldera was formed by a series of lateral gravitational collapses similar to those described in Hawaii . Evidence for the latter theory has been found in both onshore observations and marine geology studies . </P> <P> From around 160,000 years ago until the present day, the stratovolcanoes of Teide and Pico Viejo formed within the Las Cañadas caldera . </P> <P> Teide last erupted in 1909 from the El Chinyero vent, on the Santiago Ridge . Historical volcanic activity on the island is associated with vents on the Santiago or northwest rift (Boca Cangrejo in 1492, Montañas Negras in 1706, Narices del Teide or Chahorra in 1798 and El Chinyero in 1909) and the Cordillera Dorsal or northeast rift (Fasnia in 1704, Siete Fuentes and Arafo in 1705). The 1706 Montañas Negras eruption destroyed the town and principal port of Garachico, as well as several smaller villages . </P> <P> Historical activity associated with the Teide and Pico Viejo stratovolcanoes occurred in 1798 from the Narices del Teide on the western flank of Pico Viejo . Eruptive material from Pico Viejo, Montaña Teide and Montaña Blanca partially fills the Las Cañadas caldera . The last explosive eruption involving the central volcanic centre was from Montaña Blanca around 2000 years ago . The last eruption within the Las Cañadas caldera occurred in 1798 from the Narices del Teide or Chahorra (Teide's Nostrils) on the western flank of Pico Viejo . The eruption was predominantly strombolian in style and most of the lava was ʻAʻā . This lava is visible beside the Vilaflor--Chio road . </P>

When did the volcano in tenerife last erupt