What does burning of the Island Symbolize

There are a few things we can consider here. There are many Biblical allusions in this story. The burning fire at the end has turned the island into a literal and figurative Hell. The fire on the island is described by Golding as an animal unleashed by the boys eaten and growing. It can represent a tangible evil inside man unleashed. It is an evil that is all consuming. Had the boys not been saved by the navy man, all most certainly would have perished.