Hells Bells are hollow bell- or cone-shaped structures of carbonate that can reach lengths of . They are found underwater in El Zapote cenote in Quintana Roo, Mexico, on the Yucatan Peninsula; similar formations exist in other caves. In a certain depth range, such structures cover the entire surface of the cave including submerged tree trunks and other Hells Bells, although they never touch each other.
The Hells Bells are speleothems that appear to have formed through incompletely understood complex interplays between water of the cave, microorganisms living in the cave, and the surface of the Hells Bells. The name refers both to their shape and their environment, and also to a song of the same name.
Name
The name is a reference both to the shape of the structures and the lightless and toxic environment they are found in, and also to the song "Hells Bells" by AC/DC, and was proposed by cave divers. In Spanish they are called .
Appearance and site
The Hells Bells are found underwater at depths of and have the forms of conical, hollow protrusions with shapes resembling bells, lampshades, tongues, trumpets, or trunks that hang off a surface and widen downward like a cone or bell. They cover the entire surface area of the cave, including larger specimens and tree trunks; nested forms are also common, but there is always some separation to adjacent surfaces away from the attachment point. Their surface is covered with irregularities such as granules, knobs, nubs, protrusions, pustules, and swellings and sometimes by flowstone produced by exposure to air; they are generally not smooth. Some of these structures are "bubble trails"; these are channels or clefts carved into limestone by carbon dioxide bubbles.
Hells Bells are usually elliptical or circular, with their lower surface strictly horizontal and usually with a lateral gap that gives them a horseshoe outline; this opening always faces the walls of the cave and in general the Bells tend to grow away from obstacles. The angle at which a Bell opens is usually the same over its entire length. They are large: their length can exceed and their width can reach , while their walls are up to thick. The Bells that formed on tree trunks are smaller and have shapes resembling balconies or consoles. In cross-cuts, the Bells are layered, with white to yellow to brown layers that are formed in part by blade-like calcite crystals that can reach length and in part by non-crystalline layers. Manganese oxide forms brown coats on some shallower specimens.
Hells Bells are in the El Zapote sinkhole (cenote), a water-filled bottle- or hourglass-shaped cavern, more specifically in its wide cavern. At the bottom of the cavern lies a debris mound; strong rain can sweep material into the sinkhole, including some submerged tree trunks that are up to long and leaves and other plant remains that cover the floor of the sinkhole. A shaft rises to the surface to the actual sinkhole and is about wide there, while the submerged cavern reaches a width of over ; there is no detectable flow of water in the deeper cavern. Sinkholes such as El Zapote are common in the wider region and form through the collapse of caves.
Their existence has been known to the local cave-diving community for a long time, and there is a visitor centre at El Zapote where a specimen taken from the cave floor is exhibited. The Hells Bells were researched by Wolfgang Stinnesbeck from the University of Heidelberg who was investigating caves for traces of human civilization and who authored the first academic work on them.
Location
El Zapote and the Hells Bells are in southeastern Mexico, in the state of Quintana Roo west of Puerto Morelos and south of Cancun; the sinkhole lies from a road that connects Mexican Federal Highway 180 and Mexican Federal Highway 307. El Zapote is on the Yucatan Peninsula, which contains one of the largest karst-cave systems in the world, including 370 caves in Quintana Roo alone; the total length of all these caves probably exceeds and some individual systems are over long.
Formation processes
Carbonate deposits (carbonate speleothems) in caves appear to usually form when evaporation or carbon dioxide escaping from water cause calcite to become saturated, which then precipitates and forms deposits. Underwater carbonate deposits are also known however and may form through biological and physical-chemical processes. The Hells Bells appear to belong to this underwater type, as there is little evidence of exposure to air on them, and water levels in the cave appear to have always exceeded the depths at which the Hells Bells developed.