Question

how are coral islands formed simple English i have to make my sister understand

Answer 1

Coral islands are formed when microscopic animals named coral polyps die and their skeletons are stacked one upon the another for years. The coral polyps tend to live on rocks and when they die, there skeletons made up of calcium carbonate is all that is left; then other coral polyps use this as their home and when they die their skeletons are also left. This happens for many years and in a course of time, these coral islands are formed.