Report on Hierro (Spain) — 18 January-24 January 2012
Smithsonian Institution / US Geological Survey
Weekly Volcanic Activity Report, 18 January-24 January 2012
Managing Editor: Sally Sennert.
Please cite this report as:
Global Volcanism Program, 2012. Report on Hierro (Spain) (Sennert, S, ed.). Weekly Volcanic Activity Report, 18 January-24 January 2012. Smithsonian Institution and US Geological Survey.
27.73°N, 18.03°W; summit elev. 1500 m
All times are local (unless otherwise noted)
Instituto Geográfico Nacional (IGN) reported that during 18-24 January the submarine eruption continued S of El Hierro Island. Mean tremor amplitude has oscillated considerably since 19 January, including abrupt changes from rather high values to periods of almost no tremor which lasted a few hours. Emissions of large steaming lava fragments were observed every day of this report period.
Thirty-two seismic events were registered during this period, most of them located in the central part of the island, extending offshore to the S, at depths between 8 and 19 km with a maximum magnitude of 2.2. Analyses of GPS deformation showed stability both in vertical and horizontal components.
Geological Summary. The triangular island of Hierro is the SW-most and least studied of the Canary Islands. The massive shield volcano is truncated by a large NW-facing escarpment formed as a result of gravitational collapse of El Golfo volcano about 130,000 years ago. The steep-sided scarp towers above a low lava platform bordering 12-km-wide El Golfo Bay, and three other large submarine landslide deposits occur to the SW and SE. Three prominent rifts oriented NW, NE, and S form prominent topographic ridges. The subaerial portion of the volcano consists of flat-lying Quaternary basaltic and trachybasaltic lava flows and tuffs capped by numerous young cinder cones and lava flows. Holocene cones and flows are found both on the outer flanks and in the El Golfo depression. Hierro contains the greatest concentration of young vents in the Canary Islands. Uncertainty surrounds the report of an eruption in 1793. A submarine eruption took place about 2 km SSW off the southern point of the island during 2011-12.