From sun-snapped shorelines to vast reef walls visible from space, coral reefs come in strikingly different shapes. Fringing reefs, atolls and barrier reefs may all be built by tiny coral animals, but their structures reveal very different relationships with land, sea and time.
Fringing reefs are attached to a shoreline and are the most common type of reef, particularly in the Caribbean. They are easy to access from the beach, but their proximity to land makes them vulnerable to pollution.
- Coral reefs guide: what is coral and coral bleaching, and species to spot
- 'Coral superhighway' spanning more than one million square kilometres found in Indian Ocean
Atolls, in contrast, are circular or horseshoe-shaped rings of reef, comprising a tough band of coral around a sandy lagoon.
Barrier reefs lie away from the shore, separated by a deep lagoon. From above, they appear long and thin (a ‘barrier’ between ocean and land) and can drop steeply off the continental shelf.
The lagoons vary in width – Australia’s Great Barrier Reef is 200km from the shore in some places.
Understanding coral structures (morphologies) has helped scientists to map reefs and work out how they develop over geological time periods. Emma Kennedy
- Does the UK have any coral reefs?
- Can the Great Barrier Reef be saved? How Australia’s indigenous peoples could hold the key
Top image © Getty
