Main Crater

Main Crater
Originally uploaded by juanerubio.

This is how the core of an active volcano looks like. It belongs to Aso-san in Kyushu, a place which I have recently talked about here.

The greenish color of the lake was due to the high concentration of sulphur and other elements, which also produce the dangerous fumes that rise above the main cone. It was relatively safe to watch this from the observation platform, since there were plenty of concrete bunkers to take shelter in case of sudden eruption and the local authorities were checking the wind direction constantly to prevent people from inhaling the toxic gases.