A cay ( / ˈ k iː , ˈ k eɪ / KEE , KAY ), also spelled caye or key , is a small, low- elevation , sandy island on the surface of a coral reef . Cays occur in tropical environments throughout the Pacific , Atlantic , and Indian oceans, including in the Caribbean and on the Great Barrier Reef and Belize Barrier Reef .
7-449: The Port Royal Cays are a small group of uninhabited islands or cays off Port Royal , Jamaica , located at 17°55′06.36″N 76°49′11.96″W / 17.9184333°N 76.8199889°W / 17.9184333; -76.8199889 and arranged in the shape of an atoll with a diameter between 4 and 5 km, and a total area of 12 km. The land area is about 0.03 km. There are eight named cays, including South Cay Rock which
14-460: A cay surface, assisted by the deposition of sea bird guano . A range of physical, biological and chemical influences determines the ongoing development or erosion of cay environments. These influences include: Significant changes in cays and their surrounding ecosystems can result from natural phenomena such as severe El Niño–Southern Oscillation (ENSO) cycles. Also, tropical cyclones can either help build up or tear down these islands. There
21-471: Is much debate and concern over the future stability of cays in the face of growing human populations and pressures on reef ecosystems, and predicted climate changes and sea level rise . There is also debate around whether these islands are relict features that effectively stopped expanding two thousand years ago during the late Holocene or, as recent research suggests, they are still growing, with significant new accumulation of reef sediments. Understanding
28-466: Is sometimes subsumed with South Cay. Gun Cay, the northernmost, is only 400 metres from the Jamaican mainland. The main cay is Lime Cay, on the northeastern rim. It measures 380 metres northwest–southeast, and is up to 80 metres wide, measuring 2 ha in area. About half of the area is wooded, the rest is sand and coral. On the western beach is a wooden hut. The individual cays, clockwise starting in
35-537: The island is called a cay ; if they are predominantly gravel , the island is called a motu . Cay sediments are largely composed of calcium carbonate (CaCO 3 ), primarily of aragonite , calcite , and high-magnesium calcite. They are produced by myriad plants (e.g., coralline algae , species of the green algae Halimeda ) and animals (e.g., coral , molluscs , foraminifera ). Small amounts of silicate sediment are also contributed by sponges and other creatures. Over time, soil and vegetation may develop on
42-583: The north: Cay The Taíno word for "island", cairi , became cayo in Spanish and "cay" / ˈ k iː / in English (spelled "key" in American English). A cay forms when ocean currents transport loose sediment across the surface of a reef to where the current slows or converges with another current, releasing its sediment load. Gradually, layers of deposited sediment build up on
49-439: The reef surface – a depositional node . Such nodes occur in windward or leeward areas of reefs, where flat surfaces sometimes rise around an emergent outcrop of old reef or beach rock. The island resulting from sediment accumulation is made up almost entirely of the skeletal remains of plants and animals – biogenic sediment – from the surrounding reef ecosystems. If the accumulated sediments are predominantly sand , then
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