Marchena

SUMMARY

Type: shield with caldera
Activity: active
Last Eruption: 1991
Rock Type: ?
Eruptive Volume: ?
Location Map from Xerox PARC
Latitude: 0.33 N
Longitude: 90.46 W

GEOLOGIC HISTORY

The Galapagos Islands lie on the Nezca plate just south of the Galapagos Ridge spreading center. They are also thought to overlie a mantle hotspot, presently beneath the volcanicly active western Galapagos Islands.

Marchena is a low, 12 x 16 km island, with a central caldera 6 km in diameter that has been nearly filled with young basalt flows.

Historic Activity: No historic eruptions had been recorded from the volcano, but several fumaroles were active and many flows appeared to be quite young.

Recent Activity: An eruption started on Sept. 25, 1991, first observed from a ship. Lava flows reached the ocean and covered much of the caldera's SW floor, suggesting that a circumferential fissure several kilometers long had been active on the W to SW rim, supplying lava to both the caldera floor and the outer flank. Lava was still entering ocean on Nov. 8, 1991.

Data Sources

• Global Volcanism Network (V. 16, No. 8 to V. 16, No. 10)
  

ADDITIONAL INFORMATION

• Link to Global Volcanism Network's Marchena Information

Last Update: 2/13/00