Image credits

• Grey crater walls and steam rising over the turquoise acid lake at Kawah Ijen: Jakub Hałun / CC BY-SA 4.0 (source)
• Turquoise acid lake on the floor of the Ijen crater, with sulphur smoke rising on the left: CEphoto, Uwe Aranas / CC BY-SA 3.0 (source)
• Layered yellow and grey rock inside the Ijen crater in morning mist: Jakub Hałun / CC BY-SA 4.0 (source)
• Ash-covered slopes inside the Ijen crater, streaked white and orange: CEphoto, Uwe Aranas / CC BY-SA 3.0 (source)
• Hikers on the rocky path down into the Ijen crater, with yellow sulphur deposits and smoke: Jakub Hałun / CC BY-SA 4.0 (source)
• Blue sulfur flames burning on the dark floor of Kawah Ijen crater before dawn: Jakub Hałun / CC BY-SA 4.0 (source)
• Mount Raung rising over a sea of cloud, seen from the Ijen trail: Jakub Hałun / CC BY-SA 4.0 (source)
• White gas billowing from yellow sulfur deposits beside the Kawah Ijen lake: Jakub Hałun / CC BY-SA 4.0 (source)
• The green hillside trail down from Ijen, with Mount Raung above the clouds on the left: Jakub Hałun / CC BY-SA 4.0 (source)
• Sulphur smoke over the miners' work area beside the turquoise crater lake, seen from above: Oakenchips / CC BY-SA 4.0 (source)
• A line of hikers walking along the bare grey crater rim of Ijen: Jakub Hałun / CC BY-SA 4.0 (source)
• Sea of cloud below green forested slopes seen from the Ijen rim in the morning: Jakub Hałun / CC BY-SA 4.0 (source)
• Rocky inner wall of Kawah Ijen crater under pink-lit gas clouds before sunrise: Jakub Hałun / CC BY-SA 4.0 (source)
• Boulders on the crater floor with sulphur smoke hiding the lake: Jakub Hałun / CC BY-SA 4.0 (source)
• Yellow-white sulphur smoke drifting over the acid lake at dawn, seen from the crater floor: Jakub Hałun / CC BY-SA 4.0 (source)
• Dawn sky over forested ridges and low cloud seen from Kawah Ijen: Christophe95 / CC BY-SA 4.0 (source)