El Chichón volcano: eruptive history

Abstract

El Chichón volcano became known worldwide after it erupted catastrophically in 1982 and killed an estimated 2,000 people. A cumulative mass of almost 8 million tons of sulfur dioxide was injected into the stratosphere. The first reconstruction(s) of the stratigraphic successions carried out at the volcano shortly after the eruption suggested a long record of eruptive activity in the geologic past. Many studies completed in the past decade, aided by 40Ar/39Ar and K/Ar dating, have confirmed that the eruptive activity indeed was long lasting, occurring from eruptive centers located several km apart, before migrating at its present position. Within this context, El Chichón might better be described as a Volcanic Complex rather than a single volcano. During the Holocene at least 12 explosive eruptions originated from the same vent that was reactivated in 1982 producing pyroclastic density currents (PDCs) along many of the same pathways as those in 1982. This chapter summarizes the spatial and temporal evolution of this volcanic complex, integrating some previously unpublished data with the existing information. The time sequence of the 1982 eruptive events has been re-examined considering records from far-away stations and eyewitnesses’ accounts that were not taken into account in previous studies, providing a more coherent time-stratigraphic framework for the 1982 eruptive sequence. Considering El Chichon’s history of past eruptions, the existence of a wide, shallow, groundwater table and the re-establishment of an active hydrothermal system after the 1982 eruption, the probability of a new phreatic/phreatomagmatic eruption may still exist.