video loop of current ash and steam events from the Colima Observatorio Vulcanológico

The Colima Volcano Deep Seismic Experiment

Colima volcano is located near the west coast of Mexico a few hours south of Guadalajara in the state of Colima. It is on the western end of the Trans-Mexican Volcanic Belt and in the midst of a long eruption cycle. While subduction beneath North America is generally believed to be the reason that Colima and the other volcanoes in the belt exist, we understand little about how individual volcanoes are fed and maintained from below.

Most of the world’s explosive volcanism occurs at widely-spaced volcanic centers along convergent margins. Basaltic magmas from the subduction wedge are channeled to volcanoes separated by tens or hundreds of kilometers and evolve into silica-rich compositions associated with dome growth, pyroclastic flows and explosive eruptions. Decades of geochemical research have outlined a suite of processes which control the chemical and spatial evolution of these volcanoes. These ideas, which rely heavily on processes in the lowermost crust, have evolved with limited input from geophysics because the deep crust has been difficult to probe with seismics, gravity, and/or electromagnetics. The Colima Volcano Deep Seismic Experiment (CODEX) is one of the first to target the deep crustal processes which create discrete volcanoes and ultimately control eruptive behavior. The CODEX array is a cooperative venture between the Geophysical Institute at the University of Alaska Fairbanks and the Universidad de Colima Observatorio Vulcanológico located in Colima, Mexico. Beginning in 2006 we will install and maintain a seismic array in the vicinity of Colima Volcano. This network will be wider than a typical volcano monitoring array and is designed to optimize seismic tomography and receiver functions of the deep crust. Teleseismic data, together with seismicity in the local crust and subducting slab, will be used to map the temperature and melt conditions beneath Colima. The results will be interpreted in the context of existing geochemical models for the Colima complex to address two primary questions. (i) Is the location and longevity of an arc volcano governed principally by diapirism in the mantle wedge or by deep crustal conditions and Moho topography? (ii) What are the relative roles of magma ponding at the base of the crust and magma storage in the lower crust in controlling the evolution of subduction basalts into more silicic arc volcanics? This project is supported by the U.S. National Science Foundation.

For more information about the science objectives, field plan and student opportunities contact Michael West at the University of Alaska Fairbanks.