Coral reefs of the Virgin Islands other coral larvae to attach to and grow on. These corals can form into three different structures; fringing reefs, which are reefs that are close to the shore, barrier reefs, which are reefs that are alongside the shore and is separated by deep water, and an atoll reef which is a coral reef that circles a lagoon or body of water. As stated, the coral reefs such as fringing reefs, deep reefs, patch reefs and spur and groove formation are distributed over three islands in the Virgin Islands which are St. Croix (Salt River Bay National Historical Park and Ecological
Coral reef and atolls do not usually form complete circles, but are broken in places by storms. Like sea level rise, a rapidly subsiding bottom can overwhelm coral growth, killing the coral and the reef, due to what is called "coral drowning". Corals that rely on zooxanthellae can die when the water becomes too deep for their symbionts to adequately photosynthesize, due to decreased light exposure. The two main variables determining the geomorphology, or shape, of coral reefs are the nature of the substrate on which they rest, and the history of the change in sea level relative to that substrate. The