Most of us would run at mile at the sight of an erupting volcano. But for photographer Olivier Grunewald, the reward of witnessing the rare and mysterious sight of Indonesia's Kawah Ijen, a volcano near East Java, was more than worth it.
Flames shoot out of cracks in the rock five metres into the air, while the sulphuric gases are responsible for creating almost surreal blue streams of lava.
To get the shots, Grunewald needed to wear a mask at all times. But the adventure was well worth it, as his spectacular images show.
Click the images to enlarge.
More: Check out more awesome and spectacular photo galleries here.