The Canarian Archipelago is a group of volcanic islands on a slow-moving
oceanic plate,
close to a continental margin. The origins of the archipelago are controversial:
a hotspot or mantle
plume, a zone of lithospheric deformation, a region of compressional block-faulting
or a rupture
propagating westwards from the active Atlas Mountains fold belt have been
proposed by different
authors. However, comparison of the Canarian Archipelago with the prototypical
hotspot-related
island group, the Hawaiian Archipelago, reveals that the differences between
the two are not as great
as had previously been supposed on the basis of older data. Quaternary
igneous activity in the
Canaries is concentrated at the western end of the archipelago, close to
the present-day location of the
inferred hotspot. This is the same relationship as seen in the Hawaiian
and Cape Verde islands. The latter
archipelago, associated with a well-defined but slow-moving mantle plume,
shows anomalies in a
plot of island age against distance which are comparable to those seen
in the Canary Islands: these
anomalies cannot therefore be used to argue against a hotspot origin for
the Canaries. Individual
islands in both archipelagoes are characterized by initial rapid growth
(the ‘shield-building’ stages of
activity), followed by a period of quiescence and deep erosion (erosion
gap) which in turn is followed
by a ‘post-erosional’ stage of activity. The absence of post-shield
stage subsidence in the Canaries is in
marked contrast with the major subsidence experienced by the Hawaiian Islands,
but is comparable
with the lack of subsidence evident in other island groups at slow-moving
hotspots, such as the Cape
Verdes. Comparison of the structure and structural evolution of the Canary
Islands with other
oceanic islands such as Hawaii and Réunion reveals many similarities.
These include the development
of triple (‘Mercedes Star’) rift zones and the occurrence of
giant lateral collapses on the flanks of these
rift zones. The apparent absence of these features in the post-erosional
islands may in part be a result
of their greater age and deeper erosion, which has removed much of the
evidence for their early volcanic
architecture. We conclude that the many similarities between the Canary
Islands and island
groups whose hotspot origins are undisputed show that the Canaries have
been produced in the same
way.
The Teide and Pico Viejo stratocones and the Northwest and Northeast Rifts are products of the latest eruptive phase of the island of Tenerife, initiated with the lateral collapse of its northern fl ank that formed the Las Cañadas Caldera and the Icod-La Guancha Valley ca. 200 ka. The eruptive and structural evolution of this volcanic complex has been reconstructed after detailed geological mapping and radioisotopic dating of the signifi cant eruptive events. A set of 54 new 14 C and K/Ar ages provides precise age control of the recent eruptive history of Tenerife, particularly Teide Volcano, the third-highest volcanic feature on Earth (3718 m above sea level, >7 km high), and unique in terms of its intraplate setting. The development of the Teide-Pico Viejo Volcanoes may be related to the activity of the Northwest and Northeast Rifts. Volcanic and intrusive activity along both rift zones may have played an important role in activating the gravitational landslide and in the subsequent growth, nested within the collapse embayment, of an increasingly higher central volcano with progressively differentiated magmas. The coeval growth of the central volcano with sustained activity along the rifts led to a clear bimodal distribution in composition of eruptive products, with the basaltic eruptions in the distal part of the rifts and phonolitic and more explosive eruptions in the central area, where the differentiated stratocones developed. Current volcanic hazard in Tenerife is considered to be moderate, because eruptive frequency is low, explosivity is modest, and the eruptive activity of the Teide stratocone seems to have declined over the past 30 k.y., with only one eruption in this period (1150 yr B.P.).
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