Faial Volcano | John Seach


(Fayal, Capelinhos)

38.60 N, 28.73 W
summit elevation 1043 m

Faial volcano is located in central Azores. The volcano contains at 2 km wide summit caldera. The Island of Faial in the Azores forms a large shield volcano, topped by a caldera, and flanked by many satellite cinder cones and maars.

Major rift zones pass through the island, and a chain of satellite volcanoes along one of them has built the western end of the island out into the sea.

1957–1958 eruption of Fayal (Capelinhos)
The eruption of Faial volcano in 1957-58 was Surtseyan-type where rising basaltic magma came into contact with sea water. The submarine eruption at Capelinhos during 1957-58 created a new island that merged with the western peninsula.

The eruption began on 27th September 1957 after 3-4 days of earthquakes. Submarine activity occurred at four submarine vents, 1.2 km to the northwest of the lighthouse at the then most westerly point of Faial island. The water depth was 70 m before the eruption. "Rooster-tail" jets were typical of Surtseyan eruptions.

A small tuff ring was built above water, and then grew large enough to exclude seawater from the vent. This changed the eruption style from phreatomagmatic to fire fountaining, and then to lava flows.

Base Surges at Capelinhos
Base surges were first observed at underwater and underground in nuclear explosions in the Pacific, where ring-like turbulent clouds spread radially at hurricane speeds (up to 30 m/s). Base-surge clouds also spread radially from many volcanic eruption columns, especially where surface or ground water mixes with the rising magma column.

A base surge was photographed at Capelinhos volcano on 10th October 1957. The eruption cloud rose to a height of 500 m, then collapsed and spread radially in a, dark gray base surge loaded with hyaloclastic debris. The base surge was gray and full of ash, and rolled rapidly out over the top of the tuff ring and across the ocean surface. The sea up to 100 m in front of the advancing surge was hit with blocks dropped from the radial plumes.

The base surge produced hurricane-like rains of mud-coated lapilli which destroyed roofs, sandblasted trees, and deposited aerodynamically shaped mounds around the bases of small trees and bushes. North of the lighthouse, surges overtopped the peaks of eroded Concheiros volcano (160-185 meters). The surges lost most of their radial velocity within 2 km of the vent. Heavy mud rains that extended 4 to 5 km over Faial Island.

1672-73 Eruption of Faial
Eruptions occurred on a rift that extends WNW from a 2-km-diameter summit caldera.

Further reading
Pimentel, A., Pacheco, J. and Self, S., 2015. The ~1000-years BP explosive eruption of Caldeira Volcano (Faial, Azores): the first stage of incremental caldera formation. Bulletin of Volcanology77(5), pp.1-26.

Zanon, V., Kueppers, U., Pacheco, J.M. and Cruz, I., 2013. Volcanism from fissure zones and the Caldeira central volcano of Faial Island, Azores archipelago: geochemical processes in multiple feeding systems. Geological Magazine150(3), pp.536-555.

Cole, P.D., Guest, J.E., Duncan, A.M. and Pacheco, J.M., 2001. Capelinhos 1957–1958, Faial, Azores: deposits formed by an emergent surtseyan eruption. Bulletin of volcanology63(2), pp.204-220.

Faial Volcano Eruptions

1957-58, 1672-73