Nassau Bay Bike

coral reefs
Training
See also: fringing reef, coral atoll, structure and distribution of coral reefs
Most coral reefs have been formed after the last glacial period when ice melting caused sea level rise and flooding on the continental shelves. This means that most coral reefs are less than 10,000 years. As communities of coral reefs have been established on the shelves, they built the reefs that grew up, the pace of rising sea levels. Reefs that has not kept pace could be drowned reefs, covered with water until there was not enough light for the survival of others.
Coral reefs are also found in the deep sea far from continental shelves and around oceanic islands such as atolls. The vast majority of these islands of the ocean reef are of volcanic origin. The few exceptions are of tectonic origin, where plate movement lifted the ocean bottom to the surface.
In 1842, Charles Darwin published his first monograph, structure and distribution of coral reefs. There, he outlined his theory of the formation of coral atolls, he conceived an idea for the voyage of the Beagle. His theory was that the atolls were formed by uplift and subsidence of the crust beneath the oceans. Darwin's theory describes a sequence of three stages of the formation of atolls. It begins with a fringing reef forms around a volcanic island off the island and grants the ocean floor. As subsidence continues, the fringing reef becomes a barrier reef, and, finally, a coral atoll.
Darwin's theory begins with a volcanic island off
As the island and go on the ocean floor, coral growth built a fringing reef, often including a shallow lagoon between the land and the main reef
As subsidence continues the fringing reef becomes a barrier reef further from the shore with a lagoon more inside
Finally, the well of the island under the sea and the reef is an atoll surrounding a lagoon open
A fringing reef can take ten thousand years to form, and an atoll may take up to 30 million years
A small atoll in the Maldives.
Darwin predicted that in each lagoon would be a basis of bedrock, the remains of the original volcano. drilling that followed proved correct. Darwin's theory followed from his understanding that the coral polyps grow in the clean seas of the tropics, where the water is choppy, but can live only in a limited water depth, starting just below the low tide. When the level of the underlying land remains the same, the corals grow around the side to form what he called fringing reefs, and may eventually develop from the bank to become a barrier reef. When the field is increasing, fringing reefs may develop around the coast, but raised reefs above sea level dies and becomes white limestone. The disappearance of the earth slowly, the fringing reefs to keep pace with growth from the top on a base of dead coral, forming a barrier reef enclosing a lagoon between the reef and the shore. A coral reef can encircle an island, and once the well of the island below sea level to an almost circular atoll of coral growth continues to monitor the level of the sea, forming a central lagoon. barrier reefs and atolls are generally not form complete circles, but are split in places by the storms. If the earth disappear too quickly or rising sea levels too quickly, the coral dies because it is below the depth of living.
In general, the two major variables determining the geomorphology, or form, coral reefs are the nature of the underlying substrate on which they rest, and the history of changes in sea level relative to the substrate.
As an example of how coral reefs are formed on continental shelves, the structure of current living reefs of the Great Barrier Reef began to grow about 20,000 years. The sea level was then 120 meters (390 feet) lower than it is today. As sea level rose, water and coral encroached on what had been on the hills.