what created the great barrier reef on the coast of austrailia

Question: what created the great barrier reef on the coast of austrailia
- Keywords:
  australia,
  coast,
  created,
  great barrier reef
Asked by knopfler to Imogen on 10 Mar 2015.
- Imogen Napper answered on 10 Mar 2015:
  
  The Great Barrier Reef is an extremely ancient, enormous host of living things, composed of living coral growing on dead coral dating back perhaps as much as twenty million years.
  
  Many generations of dead coral have built themselves into great walls of stone covered in a range of living organisms such as coral, algae, anemones, sponges, fish, worms, starfish, turtles, molluscs, snakes, crustaceans, and an extraordinary array of thousands of species of plants and animals.
  
  How amazing is that!

Question: what created the great barrier reef on the coast of austrailia