1 | Coral is formed by certain types of polyp. | |
2 | But mushroom corals, such as this one, are loners. | |
3 | A diver swims over a bed of large, round table coral. | |
4 | Using the coral data the scientists found three previous sets of large earthquakes. | |
5 | Because the corals are alive, they provide a continuous supply of material. |