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Surtsey-like Cones on Faial (September 2009)
The 1957-58 eruption of Capelinhos Volcano is one of the best observed Surtsey-like eruptions. It started on 27 September 1957, when a new island quickly grew until it collapsed on 29 October. During the first week of November another island rose from the sea, 100 metros to the east of the former. A third island grew just after the second had collapsed as well, and by 12 November it was connected by an isthmus with Faial's coast. This volcano was in violent activity for weeks. Ejecta were thrown up to 1.5 km into the air. On 16 December the magma no longer interacted with seawater. The submarine phase had ended. Thus the ash «cock-tail» eruptions changed into Strombolian ones with lava flows reaching Faial's coast. Another submarine phase started early in 1958. Ash fallout was recorded as far as 70km from the volcano. This submarine phase ended on 12 May 1958, when a lava lake appeared within the crater and lava flows covered the cone's flanks. The Strombolian phase finally ended on 24 October 1958, when the total surface area of the new volcano had reached 2.4 square kilometers. Since then, coastal erosion is reducing the cone: in the sixties ten meters per year of the volcano's flanks disappeared in the Atlantic Ocean.
The old lighthouse of Capelinhos stands on the former coastline at right. Capelinhos spatter cone rises inside the tuff cone.
A spectacular dike of Cabeco do Canto volcano crosses prehistorical tuffs on Capelinhos coastline.
Ignimbrite layers exposed by coastal erosion on the ash cone's flanks grown during the submarine phase early in 1958.
Close-up of the ignimbrite layers on the crest of the tuff cone, covered by many bombs from the Strombolian phase.
The lighthouse dominates the ash plain connecting Capelinhos Volcano to the former coastline; note the bomb in the foreground.
Capelinhos Volcano can be considered a continuation of the chain of cinder cones on Faial's WNW rift; old lighthouse at center.
Costado da Nau Volcano rises on the former WNW tip of Faial Island. It has been partially eroded by waves from the Atlantic Ocean.
This fissure is aligned with the WNW rift and was active during the eruption. It erupted molten scoria which then solidified on rocky lips.
The 150m tall spatter cone (center-right) grew inside the much larger tuff cone after May 1958 (tuff cone W rim at left); view from the E rim of the tuff cone.
On the NW tip of Capelinhos: half of the spatter and tuff cones have been already eroded by the sea. Bluish lava flows and dikes among reddish ash layers.
Another Surtsey-like cone on the southern coast of Faial: the two Crateras das Caldeirinhas of Monte da Guia are now filled by the Ocean.
Faial's summit Caldeira seen from Canto dos Saquinhos viewpoint: note the neck at left and the cinder cone at center. The last phreatic activity occurred during the Capelinhos eruption.
|Photos by Marco Fulle taken with a 10-20mm lens (reflex digicam with 16x24mm sensor).|