how are corals formed?

Answer 1

There are several theories about how coral structures are formed. Charles Darwin originally described 3 major types of coral reefs.

The first of these types is the fringing reef, an area along the shore where coral colonies have been able to grow. Fringing reefs occur close to land and often extend out to sea for long distances. The second type of reef is a barrier reef, a well defined coral zone separated from land by a lagoon. The lagoon is a shallow area with a sandy floor, patch reefs, and patches of seagrass. An atoll is the third type of reef. An atoll is a ring-like formation of reefs with a lagoon inside the ring.

According to Darwin, barrier reefs begin as fringing reefs along the shores of a volcano. Over millions of years, the volcano sinks lower into the sea and the sea level rises around the volcano. The coral grows upwards to keep from getting too far from the sunlight at the sea surface. The outward side of the coral reef grows fastest since ocean currents bring in the plankton that the corals feed on. The water on the landward side of the reef is still and there is less oceanic plankton. Here the reef is unable to grow fast enough to keep up with the rising sea level and is eventually drowned. A lagoon develops between the reef and the land, resulting in the characteristic barrier reef shape. The volcano continues sinking until it disappears under the sea surface. The result is an atoll, a ring of coral reefs surrounding the submerged, extinct volcano. Eventually sand is trapped by the reefs and sandy islands, called cays, appear. The word "keys", as in Florida Keys, derives from the Spanish word "cay."

Over the course of many years, stony coral polyps can create massive reef structures. Reefs form when polyps secrete skeletons of calcium carbonate (CaCO3). Most stony corals have very small polyps, averaging 1 to 3 millimeters in diameter, but entire colonies can grow very large and weigh several tons. As they grow, these reefs provide structural habitats for hundreds to thousands of different vertebrate and invertebrate species.

The skeletons of stony corals are secreted by the lower portion of the polyp. This process produces a cup, or calyx, in which the polyp sits. The walls surrounding the cup are called the theca, and the floor is called the basal plate. Periodically, a polyp will lift off its base and secrete a new basal plate above the old one, creating a small chamber in the skeleton. While the colony is alive, CaCO3 is deposited, adding partitions and elevating the coral.

When polyps are physically stressed, they contract into their calyx so that virtually no part is exposed above their skeleton. This protects the polyp from predators and the elements (Barnes, R.D., 1987; Sumich, 1996). At other times, polyps extend out of the calyx. Most polyps extend the farthest when they feed.

For more infor try:
http://www.oceanservice.noaa.gov/education/kits/corals/welcome.html

Answer 2

How Corals Are Formed

Answer 3

These are formed by the precipitation reaction. Exactly the corals from a group or colony in some duration of time. Then they die and again next corals are formed over it so they form layer by layer structure. This layers can give an idea about the rain fall, salinity, temperature profile. As the formation of these depends on these factors. They can also be dated by different technique by measuring the radioactive Carbon-14 isotope (Carbon dating). These corals contains mostly Carbonates of Calcium, Magnesium and Strontium etc. When it contains some impurities they become coloured.

Answer 4

:P A coral reef is an accumulation of dead corals and other organisms with a limestone skeleton, cemented together by some algal species and by physical processes. The reef builds slowly towards the surface of the water, at the rate of a few millimetres per year. Once the reef reaches sea level, the corals cannot survive, and the reef grows horizontally. Reefs build as a result of the growth of corals and other biota, and also from accumulation of sand and rubble formed when the organisms are broken down by waves and animals, such as worms and sponges, that bore into the coral. hope it helped

Answer 5

Coral is actually a living formation. It consists of millions of microscopic life forms that gather and constitute the coral
formation.

Darryl S.

Answer 6

A rocklike deposit consisting of the calcareous skeletons secreted by various anthozoans. Coral deposits often accumulate to form reefs or islands in warm seas.
Any of numerous chiefly colonial marine polyps of the class Anthozoa that secrete such calcareous skeletons.
The red-orange, pinkish, or white deposits secreted by corals of the genus Corallium, used to make jewelry and ornaments.

Answer 7

Coral reefs are made from masses of lime of carbonate built up from the sea floor by the accumulation over thousands of years of the skeletons of minute animals called polyps.

Answer 8

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c shallow clear water Coral polyps and their symbiont species such as zooxanthellae (that perform the necessary photosynthesis for successful coral growth and expansion) rely on sunlight. Sufficient sunlight for this process is only really available down to about 50 metres. Murky water would of course prevent or reduce sunlight penetration.

Answer 9

Very very slowly. They grow.

Corals are small sea anemone-like polyps, typically forming colonies of many individuals. Each polyp generation grows on the skeletal remains of previous generations, forming a structure that has a shape characteristic of the species, but subject to environmental influences.

Answer 10

organisms called corals form calcarious substances around themselves and thus corals are formed