Alcedo Volcano - John Seach


Isabela Island, Galapagos Islands,

0.43 S, 91.12 W
summit elevation 1130 m
shield volcano

Alcedo volcano is located in central Isabela Island, Galapagos Islands. It is the only volcano in the Galapagos which has erupted rhyolite and basalt lava.

Alcedo volcano contains an active, transient hydrothermal system. The volcano contains a 7 km wide caldera with fumaroles. Most of the fumaroles are
aligned along an 1.2 km zone along the southeast caldera wall. Hydrothermal activity at the volcano is moving east, which is indicated by the larger fumaroles, young explosion craters, and dead vegetation.

Alcedo's caldera has partially filled and collapsed cyclically, creating benches on the northwestern and eastern caldera walls.

Volcano Alcedo supports a population of four thousand tortoises. Flightless Cormorants can sometimes be seen on Punta Garcia.

Alcedo Geyser
This is the easternmost large fumarole, which is found in a 5 m diameter hole at the southern edge of an explosion crater approximately 75 m in diameter. The vent previously erupted water, but now only emits gas. West of Alcedo geyser crater is a relatively flat area covered with recently killed trees and shrubs.

1995 Activity
On 7th February 1995 there was a muffled explosion and earthquake experienced by scientists on the volcano. The subterranean event occurred in Alcedo's hydrothermal system, and was similar to activity in 1970.

1993 Eruption
An eruption in 1993 was not witnessed and created two new craters.

1970 Activity
In 1970, rumbles lasting 2-3 seconds, followed by muffled booms, were heard near an active geyser. The sounds were attributed to shallow steam explosions, which triggered small earthquakes.

1953 7 Eruption
An eruption occurred at Alcedo volcano, sometime between 1946 and 1960, based on aerial photos. A lava flow low was visible on the southeast flank of the volcano.

Alcedo Volcano Eruptions

1993, 1953 ± 7 years

Eruptions at the volcano originate from circumferential fissures near the caldera, and radial fissures on distal flanks.