The Canary Islands lie in an intraplate setting, on the African continental shelf. Volcanism may result form a mantle hotspot beneath the islands. The alignment of vents and fissures in the Canary Islands suggests northeast-, northwest-, and north-south-trending faults. Las Canadas Caldera is siturated at the intersection of three such fissures or rift zones, called dorsals, of which the northwest- and northeast-trending ones have been dominant in recent geologic and historical time (Carracedo, 1985).
The Las Canada Caldera formed initially by collapse following a large plinian eruption that produced the Granadilla pumice (Booth, 1973), perhaps around 150,000 years B.P. (Arana and others, 1985). Thick plinian and phreatoplinian pumice deposites occur on Tenerife (Fuster and others, 1968; Ridley, 1972; Booth, 1973; Arana and Carracedo, 1978). Subsequent gravitational failure of part of the north wall left the caldera open to the north (Booth, 1979). Pico Viejo and Teide Volcanoes have grown within the area of collapse, north of the escarpment.
The eruption of 1492 was probably from the Teide vent (Soler and others, 1984).
An eruption of Siete Fuentes on 31 January 1704 (volume 0.4 x 106 cubic meters) was preceded by 7 days of premonitory seismicity; eruptions of Volcan Fasnia on 5 January 1705 (volume 2.5 x 106 cubic meters) and of Montana Arenas on 2 February 1705 (volume 24 x 106 cubic meters) were preceded by several days of seismicity, and an erutpion of Montana Negra on 5 May 1706 (volume 66 x 106 cubic meters) was preceded by one evening of seismicity (data from F. Machado and A. Hernandez Pacheco, cited in Carracedo, 1985).
Volcan Chahorra eruption, 1798
A flank eruption along the northwest dorsal (Volcan Chinyero) in 1909 was preceded by 18 months of seismicity, including earthquake swarms in July, August, and especially November 1908. Maximum activity was 14 shocks in two hours, as felt in Orotava.
from: http://vulcan.wr.usgs.gov/Volcanoes/Can ... anics.html