The pile reaches up higher and higher as more trees are munched up and swallowed. Once the tip reaches its source, the gullet gate, the stomach contracts. The pile collapses and plant material is spread in all direction. It's fragmented enough so it doesn't do any real damage to the three inside. When the pile is down a new layer is added that reaches slightly above their feet. Stomach juice is coming in from the side steadily. If they wish to stay on top they should act now. Meanwhile a fresh pile is slowly being formed.