lava tunnel in narusawa ice cave

adventure ancient aokigahara asia bedrock below cave caves cavity chemistry circular cold crust curiosity deep depth drip drips earth environment environments eruption forest freeze freezing fuji gaps geography geological geology glacier glaciers hyoketsu ices japan japanese jukai lakes latent lava limestone loop mount narusawa nature needle pillars plates remnant remnants rocks seed spots staircase storage structural structure temperature tokyo tour tourism tourist tourists transparent traps trees tubes tunnel tunnels underground vein veins wall water wonder world zone