Geothermal pools and associated wetlands are fed by deeply circulating groundwater that mixes with magma and hot rocks in volcanically active regions. Mineral concentrations are therefore high and produce chemically precipitated substrates as waters cool. The extreme temperatures and water chemistry limit life to a low diversity of specialised bacteria, extensive algal mats and insect larvae which can live in warm acid or alkaline water with high mineral content. Away from their hottest waters, aquatic plants, crustaceans, frogs, fish, snakes and birds can all occur.