From the small University of the Azores ship Arquipelago (right) in 2003, we surveyed the coasts with a high-resolution multibeam sonar installed beneath the vessel's bows. The data revealed remarkable branching lava structures such as those shown below. We interpreted these as the lava repeatedly arrested by enhanced cooling at the flow front where fractures are continually opened but then repeated repressurisation within the lava causes it to break out somewhat like pahoehoe lava on land. More details:
Mitchell, NC, C Beier, P Rosin, R Quartau, F Tempera, Submarine lava flows around the coasts of Pico Island, Azores, Geochem. Geophys. Geosyst., 9, Q03024, doi:10.1029/2007GC001725, 2008. |
The computer-generated image above shows lava flows in 3D along the southeast coast of the island. The flows to the left show branching geometries to the northwest of the Pico and offshore an area where a lava flow entered the sea in 1718 AD. |
Landslides are dramatic features of both island groups, and the slope analysis
showed that some debris avalanches (fast-moving landslides) have similar
characteristics in both islands groups, implying similarities in flow process. However, the Hawaiian islands contain blocks
of far greater size than in the Canaries and the paper discusses possible origins
for this difference. For those areas that are not obviously affected by landslides
(areas we called constructional slopes), within the flanks of the Canary islands
we observe mostly sharp cones. Only
rarely do we observe terraces such as those shown here (from the deep slopes of
El Hierro island) which are similar to terraces commonly observed around Hawaiian
rift zones.
Further notes on the Canaries can be found on the
Oxford pages
Relevant publications
Funding for the above work was provided by Research Fellowships
from the Royal Society and the NERC. The field work around the Canaries was
supported by grants to Masson and Watts from the NERC. The TOBI field work around
the Azores islands was supported by the European Union (EASSS) and
by the CNR, Italy for the TOBI project, and for the multibeam project
by the Royal Society, British Council, HEFCW (equipment) and Portuguese research agencies.
*The American Geophysical Union owns the copyright to these documents. Further reproduction or electronic distribution of them is not permitted.
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