Lake Eacham ("Yidyam") was formed over 9,130 years ago when molten magma from the Earth's mantle rose to the surface and heated the water table. The steam that resulted from the boiling water was trapped underground, until massive explosions signalled its release. Huge cracks appeared in the ground and the trees that once lathed the mountainside were levelled and burnt. Eventually, after the eruptions, groundwater filled the crater and the trees grew back, creating the tranquil lake used today by families and tourists for recreation. There are no streams that flow into or out the lake, water is only lost through soakage and evaporation and only replenished through rainfall, the level can fluctuate up to 4 metres between wet and dry seasons. The nearby Lake Barrine formed in a similar way, over 17,300 years ago.