Skip to Main Content
Book Chapter

Large hydromagmatic eruption related to Fernandina Volcano’s 1968 caldera collapse—Deposits, landforms, and ecosystem recovery

By
Keith A. Howard
Keith A. Howard
U.S. Geological Survey, MS-973, Menlo Park, California 94025, USA
Search for other works by this author on:
Tom Simkin
Tom Simkin
Department of Mineral Sciences, Smithsonian Institution, Washington, D.C., 20013-7012, USA
Search for other works by this author on:
Dennis J. Geist
Dennis J. Geist
National Science Foundation, 2415 Eisenhower Avenue, Alexandria, Virginia 22314, USADepartment of Geology, Colgate University, Hamilton, New York 13346, USA
Search for other works by this author on:
Godfrey Merlen
Godfrey Merlen
Puerto Ayora, Galápagos Islands, Ecuador, 200350
Search for other works by this author on:
Bruce Nolf
Bruce Nolf
Cove, Oregon, USA
Search for other works by this author on:
Publication history
12 March 201819 September 2018

ABSTRACT

The hydromagmatic eruption that immediately preceded the 1968 caldera collapse of Fernandina Volcano, Galápagos, which had a volcano explosivity index (VEI) of 4, offers a case study of powerful eruptions where basaltic magma interacts with caldera-ponded water. The 4-d-long hydromagmatic eruption sequence records an early stage and a small fraction of the volume of magmatic withdrawal that led the caldera floor to lower 350 m over the next 10 d. Erupted tephra was lithic-rich. The small proportion of juvenile basaltic glass included blocky fragments, Pele’s tears, and Pele’s hair. Pyroclastic density currents swept across the western summit plateau 600–700 m above the vent and deposited dunes, cross-bedded and rubbly breccia deposits, imbricated lag blocks, and ash plasters, and toppled trees. Blocks ejected out of the caldera formed impact craters on the volcano’s flank >600 m higher and >1 km away. Ejected blocks are mostly basalt but include cumulate olivine gabbro. The vent area enlarged by 300 × 106 m3 during the eruption. A small adjacent fault-bounded block subsided after the eruption. Lake water and groundwater confined within the caldera by ring dikes were available to interact with hot rocks and magma. In our interpretation, this water helped to trigger and feed the eruption by interacting with rocks above a lowering magma column. Ecosystems recovered rapidly on the tephra. Eruptions have not diminished the island’s biodiversity despite Fernandina’s high rate of volcanic activity, including the massive resurfacing in 1968. Stratigraphic evidence suggests that the 1968 eruption may be only the latest in a series of explosive eruptions from the caldera.

You do not currently have access to this article.

Figures & Tables

Contents

GSA Special Papers

Field Volcanology: A Tribute to the Distinguished Career of Don Swanson

Geological Society of America
Volume
538
ISBN electronic:
9780813795386

GeoRef

References

Related

Citing Books via

Close Modal
This Feature Is Available To Subscribers Only

Sign In or Create an Account

Close Modal
Close Modal