Encyclopedia of Islands

image image image image image image

Volcanism in the Canary Islands

The age of volcanism in the Canary Islands is well known from radiometric age dating. More than 600 K/Ar, Ar/Ar, and 14C ages have been obtained by different groups on igneous samples from the islands. There have been a number of problems, however, primarily in dating older volcanic rocks and the uplifted portions of the seamount formations, some of which are clearly affected by alteration. Samples with excess Ar have produced ages that are too old, artifi cally increasing the duration of the basaltic shield stage on the islands. Ages obtained by newer techniques, such as Ar/Ar step heating, single crystal laser age dating, and the K/Ar unspiked method, and the employment of stringent age-dating requirements (e.g., sampling from well-controlled stratigraphic sections, and performing replicated analyses and systematic comparison of the palaeomagnetic polarities of the samples with the currently accepted geomagnetic reversal timescales) demonstrate
that there is a progression of increasing age of the shield stage of volcanism from west to east in the Canary archipelago and from southwest to northeast in the Canary volcanic province, even though most of the Canary volcanoes have had a very long, complicated history, often including multiple cycles of late-stage volcanism (Figs. 1 and 2).

VOLCANIC HAZARDS

Geological hazards are moderate in the Canary Islands compared, for instance, with the Hawaiian Islands, which have a similar area and population but much more frequent and intense volcanic activity and seismicity. Although high magnitude eruptions (plinian) occurred in the geological past of the Canarian archipelago, only moderately explosive activity (strombolian to subplinian) took place in the last 200,000 years. Holocene eruptions, predominantly basaltic fi ssure eruptions, occurred on all the islands except La Gomera and Fuerteventura. Most of these, however, have been located on La Palma, El Hierro, and Tenerife, with only 10–12 events on Gran Canaria during this period and two on Lanzarote (1730–1736 and
1824).

Volcanism in the Canary Islands

The most recent eruption in the Canary Islands was in 1971, from the Teneguia volcano at the southern tip of La Palma. During the Holocene, phonolitic strombolian to subplinian eruptions were associated with lava dome growth in the Teide volcanic complex on Tenerife, and to a lesser extent on the Cumbre Vieja rift on La Palma.No casualties have been reported in the 16 eruptions recorded after the colonization of the archipelago at the end of the sixteenth century. Reliable prediction of when future eruptions will occur is not feasible because of the low frequency of events and great variability of inter-eruptive periods, from a few years to several hundred years (e.g., on Cumbre Vieja, the most active volcano in the historic epoch, repose periods varied from 26 to 237 years).