An underground river
This sapphire-colored pool in the Cayo District is a geological feature known as a karst window. It is an exposed segment of a subterranean river, showing the underground drainage systems that riddle the limestone bedrock of Belize. The feature was created when the roof of a cavern in an underground river system collapsed, unroofing a portion of the channel. This specific karst window is part of St. Herman's Blue Hole National Park, a protected area of over 500 acres.
The water in the Blue Hole is part of a larger network. An underground branch of the Sibun River flows through the extensive St. Herman's Cave system, disappears beneath the surface, and reemerges in this tranquil pool before vanishing once more into the limestone underworld. This process is characteristic of karst topography, a landscape formed by the dissolution of soluble rocks like limestone. The constant flow of slightly acidic water carves and enlarges subterranean passages over millennia, creating vast networks of caves and underground rivers.
Dimensions and ecology
The Blue Hole itself is a cenote, or sinkhole, that forms a pool about 25 feet (8 meters) deep at the base of a larger depression that is roughly 300 feet (91 meters) in diameter. The bright blue color of the water is a result of its depth and the natural filtration it undergoes as it travels through the limestone cave system.
The pool is a popular spot for a cool swim, as its water maintains a refreshing temperature year-round. The park that contains the Blue Hole is an important habitat for a diverse range of wildlife. The surrounding broadleaf forest hosts over 200 species of birds, including the Slaty-Tailed Trogon and the Red-legged Honeycreeper. Mammals such as jaguars, ocelots, and jaguarundis have also been recorded within the park's boundaries.