hot grey mud river flow with an orange sulfuric soil hills around in hverir, myvatn geothermal area in iceland

area boiling branch colorful crack crater creek crevasse field fissure flood flow formation geology geothermal grey hill hot spring hverarapara hverir iceland icelandic lake landmark landscape mineral moon mountain mud myvatn natural nature orange pool red river rock simmering soil solfataras steam stream sulfur sulphating sulphur tourist volcanic water sulfuric hills iceland