How is it continually surviving?

The Great Barrier Reef is an oceanic jewel located in the eastern coast of Queensland, Australia, and is the largest system of coral reefs found on Earth. It is a geological feature that is half alive (corals, sponges, shellfish, fish, etc.) and half inanimate (calcium carbonate rocky reefs). Was this Great Barrier Reef always there? How old is it? How in the world this geologic and biologic feature formed? How is it continually surviving? Why is it so amazingly long (about 1,400 miles) and why is it considered the largest biologically created structure in the world? Is this planetary place biodiversity-poor or biodiversity-rich? Why? Why is the Great Barrier Reef in the place where it is right now and not in, say, India? Is the Great Barrier Reef dying, or is it still growing? How can you visit and study the Great Barrier Reef? Can the Great Barrier Reef exist without humans? Do we get anything from the Great Barrier Reef?Investigate about the Great Barrier Reef and write an essay about it.