Skip to content

What is causing the El Chichón crater lake non-seasonal large-size variations?

María Aurora Armienta1, Ángel Gómez2, Silvia Ramos3, Servando De la Cruz-Reyna1

  • Affiliations: 1 Instituto de Geofísica, Universidad Nacional Autónoma de México, Ciudad de México, Mexico; 2 Centro Nacional de Prevención de Desastres, Ciudad de México, Mexico; 3 Universidad de Ciencias y Artes de Chiapas, Tuxtla Gutiérrez, Chiapas, Mexico

  • Presentation type: Talk

  • Presentation time: Friday 09:00 - 09:15, Room S150

  • Programme No: 6.8.3

  • Theme 6 > Session 8

Abstract

A few weeks after the major explosive eruption of El Chichón volcano in 1982, which caused the worst volcanic disaster in Mexico, a lake formed on the floor of the 1 km wide, 200 m deep crater carved by the intense explosions. Since then, discontinuous yet persistent monitoring of various geophysical and geochemical parameters revealed different interaction regimes between the lake and the underlying hydrothermal and magmatic systems. In particular, the correlations between the evolution of some hydrogeochemical parameters like pH, B, and Cl- and the varying crater lake area revealed significant changes in the magmatic and hydrothermal influence on the lake water. Distinctly different changes in those regimes have been recognized in 1983 and 2002. Identifying the causes of the regime changes represents a critical problem for assessing volcanic hazards. Searching for possible origins of the hydrogeochemical and lake size variations, we inferred that the loss of permeability of the interface between the lake and the underlying systems caused the first regime change in 1983. Then, we analyzed several other possible causes for the second change, including the seismicity within 12 km around the volcano. We found that in the period 1990-2006, only one M 4.0 earthquake was recorded in that area on October 9, 2002. This event may have altered the degree of interaction between the lake water and the hydrothermal system,  modifying the stress and displacement in two fractures crossing the volcanic edifice: Chichón-Catedral (NW-SE) and San Juan (E-W) faults.