Red algae are important builders of limestone reefs.

This structure was built from granite boulders placed on top of an existing limestone reef.

A limestone reef between the island and shoreline presents a safety hazard for watercraft that draw more than 3 feet.

El Capitan is the southern terminus of the Guadalupe escarpment, an ancient limestone reef that forms the present-day Guadalupe Mountains.

Hard and soft corals, along with sponges, cover the numerous limestone reefs.

The original limestone reefs constitute the essence of the rugged character, rough and impressive of Sierra de Aralar.

Detrital sediments were washed in by rivers from the continent, over the limestone reefs which formed the shallow sea floor.

The boundaries of the reserve were extended in 1993 to include the adjacent limestone reef of Horseshoe Reef at Christies Beach.

Due to its limestone reefs with its rough texture, underwater walls are often scattered with colourful sponge walls.

The core of the mountain is formed by an oncoidal limestone reef covered by successive pelagic carbonate deposits including ammonite beds.