Marchena Volcano | John Seach

john

Galapagos Islands, Ecuador

0.33 S, 90.47 W
summit elevation 343 m
shield volcano

Marchena volcano is located in the northern Galapagos Islands.

Marchena is a shield volcano covering an area of 126 sq km. The summit is located on the NE rim of a shallow 6 x 7 km wide caldera. Marchena volcano is located relatively far from the center of the hot-spot, and the morphology suggest that the volcanic activity is decreasing.

Magmas at the volcano is possibly derived from melting of the Galapagos plume mixed with magmas of the Galapagos Spreading Center.

Caldera formation
The caldera is one of the largest in the Galapagos Islands. The caldera has nearly
been filled with younger flows, except for a small segment of the southwestern rim where the pre-caldera lavas are visible. The age of the caldera is unknown. The caldera possibly formed in successive stages of subsidence followed by periods of inflation of the volcano.

1991 Eruption
The first eruption in about 1000 years occurred at Marchena volcano on 25th September 1991. The eruption was observed from a ship 75 km south of the island. A glow was visible at night, and grey emissions during the day. On 28th September lava was observed flowing into the sea over a 1.5 km wide front on the west coast.

Previous eruptions
Periods of explosive activity have been common throughout the history of the volcano. Post-caldera basaltic tephra covers about 23% of the island. The most active post-caldera vents are fissures and spatter cones on the north-nortwestern rim of the caldera.

Marchena Volcano Eruptions

1991