The volcano’s crater is one mile in diameter and contains two lakes. The northern lake, Laguna Caliente (Hot Lake), is extremely acidic (nearly, 0 pH). This green water is very hot, with temperatures ranging from, 22C to 94C (71F to 201F). Some of the water filters through many layers of volcanic soil purifying it. Then it is heated in the volcano before it flows out. It both forms one of the Rincon de la Vieja’s rivers and appears as hot springs, bubbling to the surface through underground fissures in the earth’s crust at Blue River Resort & Hot Springs, located beside the 34,800- acre (14,084 ha) Rincon de la Vieja National Park, in Guanacaste.