Primary succession starts and there is NO soil just rocks that maybe volcanic. After weathering and lots of change happens there soon is soil again. After a while it soon goes back to a forest with a stable ecosystem. Then another catastrophic event happens only leaving soil which is secondary succession. After a while some plants start to grow back and some of the animals that used to live there come back and they are called the pioneer species. Finally everything is back to equilibrium and the ecosystem is a climax community.