A photographic method for detailing the morphology of the floor of a dynamic crater lake: the El Chichón case (Chiapas, Mexico)

Abstract

The active volcano El Chichon (Chiapas, Mexico) hosts a shallow acidic crater lake. During the period 2001–2007, 26 photographs of the crater lake were taken from the same spot at the eastern crater rim, ~160 m above the crater floor. The size of the lake was extremely variable. Using a GPS track from around the lake shore as a reference, 26 digitized lake outlines were corrected simultaneously for the perspective angle. The corrected lake outlines were superposed, leading to a “morphological map” of a large section of the lake bottom. This map provides insight into the erosive–sedimentary regime of the lake floor. The inner section of the lake is more stable due to the precipitation of sealing clays. This is probably one of the reasons why the El Chichon crater lake has never disappeared during the past 28 years. The sealing clays at the lake bottom can be considered the superficial analog of impermeable clay caps at the depths of hydrothermal systems. The photographic procedure presented here may be useful for other limnological and (volcanic) lake studies aimed at describing lake morphology, and for eventually deducing the surface area and volume of the lake.