Marchena

Photo of this volcano
  • Country
  • Volcanic Region
  • Primary Volcano Type
  • Last Known Eruption
  • 0.33°N
  • 90.47°W

  • 343 m
    1125 ft

  • 353080
  • Latitude
  • Longitude

  • Summit
    Elevation

  • Volcano
    Number

Most Recent Bulletin Report: October 1991 (BGVN 16:10) Citation IconCite this Report


Flow front advances into sea with no explosive venting

[The eruption] has continued without explosive venting visible from a distance. Observers on a boat that passed Marchena on 7 or 8 November reported vigorous steaming at the W coast. Water near the flow front was too hot to touch and numerous fumaroles were evident inland. Since David Day's 28-30 September visit, lava had formed a single broad front at the coast, closing the small bay where Day had landed.

Reports collected by Day provided additional information about the timing and characteristics of the early phases of the eruption. The first reported activity was a "suspicious" large cloud seen over Marchena on 25 September at 1840 from ~65 km S (at Bartolomé). An explosion was observed at 1905 from ~90 km SSE (Turtle Cove, Santa Cruz Island). A low white cloud near the coast was seen with infrared binoculars at about 2100. Witnesses at three sites ~65 km S reported 7-8 evenly spaced vents that remained active throughout the night. Incandescent ejecta appeared to rise roughly the equivalent of the island's elevation (~350 m), with height increases of ~25% during the strongest activity. A more vigorous vent, lying W of the others, was first seen at about 0300 on 26 September. Ejecta heights from the W vent appeared to exceed those from the other vents by ~50%.

Information Contacts: D. Day, Isla Santa Cruz.

The Global Volcanism Program has no Weekly Reports available for Marchena.

Bulletin Reports - Index


Reports are organized chronologically and indexed below by Month/Year (Publication Volume:Number), and include a one-line summary. Click on the index link or scroll down to read the reports.

08/1991 (BGVN 16:08) First historical eruption

09/1991 (BGVN 16:09) Lava from circumferential fissure flows into caldera and ocean

10/1991 (BGVN 16:10) Flow front advances into sea with no explosive venting




Information is preliminary and subject to change. All times are local (unless otherwise noted)


August 1991 (BGVN 16:08) Citation IconCite this Report


First historical eruption

Marchena . . . started erupting on 25 September. The TOMS instrument aboard the Nimbus-7 satellite passed at about 1100 and sensed no SO2, but the next pass, at the same time on 26 September, mapped a 300-km plume to the SW with an SO2 content estimated to be close to 100 kt. High SO2 values immediately over the volcano indicated that the eruption was still vigorous at that time. On the following day the plume was nearly twice as long, but had almost vanished by the same time on 28 September. Weather satellite images during this period showed low cloud cover, but no conclusive indication of the volcanic plume. . . .

Information Contacts: A. Carrasco, Charles Darwin Research Station; S. Doiron, GSFC; SAB.


September 1991 (BGVN 16:09) Citation IconCite this Report


Lava from circumferential fissure flows into caldera and ocean

The eruption was first observed on 25 September at about 2100 from a ship ~ 75 km S of Marchena [but see 16:10], and glow remained visible through the night. A large black and white eruption cloud was reported the next day, but no glow was evident during cloudy weather that night from a nearby island. During an overflight around midday on 27 September, a dark plume was visible above low weather clouds.

When David Day and others arrived at the island's W coast on 28 September at about 2230, lava was flowing into the sea along a front ~1.5 km wide. Incandescence was evident at about 10 sites over a roughly 3 x 3 km area, but lava fountaining had apparently stopped. The next day, small quantities of Pele's hair were found on the beach near the fresh flows, along with substantial numbers of dead fish and other marine organisms. Scuba divers found glassy breccia near the shore, a zone of aa rubble extending seaward for several hundred meters, and, with gradual increase in slope from 25 to 35 m depth, a small lava flow that included pillow structures. A 30 September summit climb revealed new lava covering 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.

Information Contacts: D. Day, Isla Santa Cruz.


October 1991 (BGVN 16:10) Citation IconCite this Report


Flow front advances into sea with no explosive venting

[The eruption] has continued without explosive venting visible from a distance. Observers on a boat that passed Marchena on 7 or 8 November reported vigorous steaming at the W coast. Water near the flow front was too hot to touch and numerous fumaroles were evident inland. Since David Day's 28-30 September visit, lava had formed a single broad front at the coast, closing the small bay where Day had landed.

Reports collected by Day provided additional information about the timing and characteristics of the early phases of the eruption. The first reported activity was a "suspicious" large cloud seen over Marchena on 25 September at 1840 from ~65 km S (at Bartolomé). An explosion was observed at 1905 from ~90 km SSE (Turtle Cove, Santa Cruz Island). A low white cloud near the coast was seen with infrared binoculars at about 2100. Witnesses at three sites ~65 km S reported 7-8 evenly spaced vents that remained active throughout the night. Incandescent ejecta appeared to rise roughly the equivalent of the island's elevation (~350 m), with height increases of ~25% during the strongest activity. A more vigorous vent, lying W of the others, was first seen at about 0300 on 26 September. Ejecta heights from the W vent appeared to exceed those from the other vents by ~50%.

Information Contacts: D. Day, Isla Santa Cruz.

Eruptive History


Summary of Holocene eruption dates and Volcanic Explosivity Indices (VEI).


Start Date Stop Date Eruption Certainty VEI Evidence Activity Area or Unit
1991 Sep 25 1991 Nov (?) Confirmed 2 Historical Observations West to SW caldera rim

This compilation of synonyms and subsidiary features may not be comprehensive. Features are organized into four major categories: Cones, Craters, Domes, and Thermal Features. Synonyms of features appear indented below the primary name. In some cases additional feature type, elevation, or location details are provided.

Photo Gallery


The low shield volcano forming Marchena Island contains one of the largest calderas of the Galápagos Islands. A group of pyroclastic cones was constructed inside the caldera. Lava flows originating from the 6 x 7 km wide caldera have spilled through low points on the caldera rim and flowed down the flanks of the volcano, in some cases reaching the sea. The first historical eruption of Marchena occurred in 1991.

Aerial photos by Instituto Geográfico Militar (courtesy of Minard Hall).
See title for photo information.
A large tuff cone rises near Punta Calle on the southern coast of Marchena Island beyond fresh-looking lava flows west of the cone in the foreground. The low shield volcano forming Marchena Island contains one of the largest calderas of the Galápagos Islands. In contrast to other Galápagos volcanoes, the 6 x 7 km caldera and its outer flanks have been largely buried by a cluster of pyroclastic cones and associated lava flows. The first historical eruption of Marchena occurred in 1991.

Photo by Ed Vicenzi, 1984 (Smithsonian Institution).
See title for photo information.

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