Coralloids are one of the most common forms of cave formation and can take a variety of forms, as shown in the photos. The term encompasses all manner of knobby, globular, button-like, coral-like, or botryoidal-type formations that can form either above or below water. One of the most common resembles popcorn and is often given that name, so we have a whole separate page devoted to it.
Death coral (lower photo) is an unusual form of coralloid found in the caves of the Purificacion area in northern Mexico. They occur in a great many shapes and sizes, always on the floor. The reason for their unique forms is not clear, as their means of formation is speculative. Most coralloids develop above water, from thin films of seeping, calcite-laden water. Since dead coral is always found on the floor, they are most likely formed below water. On the other hand, subaqueous coralloids tend to be more rounded, while death coral is, as the name implies, sharp-edged. The mystery of death coral’s formation is a problem waiting to be solved.
AUTHOR: Dave Bunnell