Since the beginning of the recent eruption, a dense plume of water vapor, gas, and ash has concealed the summit of the Nabro volcano.

Exhaling clouds of gas, a cauldron of lava boils in the mile-wide crater of Nyiragongo, an active volcano in the Congo that threatens two million people.

The eruption seems to have started with the volcano spitting out lumps of rock up to 2 metres across, before releasing an enormous pyroclastic flow - a fast-moving gush of hot gas and rock.