wall of the lava tunnel (raufarholshellir), close-up view of the dripstone red and brown iron volcanic rocks, iceland

underground activity basalt cave color deposit detail dripstone eruption flow formation geologic geology iceland icelandic illuminated inside interior iron laitahraun landmark lava tube tunnel layer magma material metal microorganisms mineral natural nature peninsula raufarholshellir red reykjanes reykjavik rock stone surface tourism tourist travel view volcanic volcano wall