The Arenal volcano is almost symmetrically perfect. It has the distinction of being one of the most active volcanoes in Costa Rica. Columns of ash are usually expelled daily.
In July 1968, three craters on the volcano's western flank burst open. This marked the beginning of an eruptive period for the volcano. That year, a flow of hot rocks and toxic gas was emitted from Crater A. The flow covered 7.5 miles and devastated nearby towns. In September 1968, Crater A also began to emit lava. In 1973, the volcanic activity moved from Crater A to Crater C, where it reached altitudes of 1,450 meters.