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Coral Reefs


§        Coral reefs are made of the skeletons of coral animals

o       Coral animal is a polyp like animal with a calcium carbonate skeleton

o       They form over thousands of years


§        Coral animals are relative of jellyfish

o       Most are smaller than your finer nail

o       They grow in shallow tropical water

o       They live on algae that grows in their bodies – symbiotic relationship

o       Coral animals absorb calcium from the ocean water.  It combines with carbon and oxygen to form  the mineral calcite

o       When coral animals die they leave behind their skeletons – as they pile up a coral reef is born.


§        Limestone reefs – All coral reefs are organic limestone.

o       Limestone deposits that began as coral reefs provide evidence of how plate motions have changed Earth’s surface.

o       Deposits of organic limestone in areas that are dry prove that at one time that land was covered by oceans.

o       We have many limestone deposits in Wisconsin, Illinois, Indiana, Texas, New Mexico


§        Why are they important

o       They are important because they form the habitat for many larger animal species