* Limestone: Coral skeletons are made primarily of calcium carbonate, which is the same material as limestone.

* Animals: Corals are tiny marine animals called polyps.

* Skeletons: Over time, as generations of corals grow and die, their skeletons accumulate, creating a massive, layered structure.

* Island Formation: These structures, called coral reefs, can grow so large that they break the surface of the water, forming islands or atolls.

Types of Islands Formed from Coral Skeletons:

* Fringing reefs: These reefs grow close to the shore.

* Barrier reefs: These reefs are separated from the shore by a lagoon.

* Atolls: These are ring-shaped reefs that enclose a lagoon.

Interesting Facts:

* The Great Barrier Reef in Australia is the largest coral reef system in the world.

* Coral reefs are incredibly biodiverse ecosystems, supporting a wide range of marine life.

* Climate change and ocean acidification are significant threats to coral reefs.

Let me know if you have any other questions about coral reefs or island formation!