This floating island is pretty common due to really old floating islands withering away the older it gets. At stage 1 of old age, trees lose their leaves and the water changes colour. In stage 2, the trees are unstable and fall off the island causing raining trees, also the water evaporates completely. In stage 3 (This stage), the cave crumbles down and the rocks fall off the island causing another disaster called 'preciperocktion' or raining rocks. The word comes from words 'precipitation' which means rain, and 'rock'. The final stage (Stage 4) is where the iisland itself withers away, its remains are fed to the other living floating islands to live longer.
