How old are coral reefs?

Coral reefs are extremely old. Corals probably existed as long as 350million years ago. That's 100 million years before the first dinosaurs walked the Earth.

The reefs we can see today have been around for over 50 million years, which means that they were being built by little corals quite soon after the dinosaurs became extinct. Pretty amazing isn't it?

Coral reefs are often very big, but it takes them a long time to get to that size. Large corals only grow between 5mm and 25mm a year. Smaller corals are faster, adding as much as 20cm to their branches each year.Even at this speed, building something the size of a coral reef takes a very long time.