Caldera Lake

Made for Build-a-Map Contest 5. A map centered around a massive volcanic caldera, now filled with water in a lush lake. But the island in its center, despite being a prime location for a new colony, hints that the volcano is not as dormant as the beavers may hope. The mountain itself is riddled with channels and old lava-flow passages, shunting water and bad-water across the map. With the caldera's ridge overhanging the lake, escape may be difficult, but the beavers are clever and crafty, and once on the top of the Caldera, the entire mountain is their oyster. Travel across the Caldera is a breeze with new transportation technology. Can you seal the caldera against bad-water contamination? Or will you abandon the lake entirely and build around the ridge? (Tested and beaten in hardcore mode with the Folktails)