Mount Ruapehu lahar. Satellite image of Mount Ruapehu, New Zealand, during a lahar flow. North is at top. Vegetation is green, cloud cover (left and bottom) is white, rock is purple/grey, water is blue and snow is white. A volcanic lake situated near the summit of the volcano appears lilac. From this lake a lahar (lilac), a mudflow composed of pyroclastic material and water, is flowing down the eastern flank of the volcano. Lahars are extremely dangerous because of the speed at which they flow. This particular event, which began on 18th March, did not result in any fatalities. Image obtained by the ASTER satellite on 25th March 2007.