NUEE ARDENTE

(French: fiery cloud, or glowing cloud), highly destructive, incandescent mass of gas-enveloped volcanic particles that is associated with Pelean eruptions. These glowing avalanches, as they are sometimes called, can move very quickly down even slight inclines and may attain speeds as great as 160 km (100 miles) per hour. The temperature of the volcanic gases can reach about 600 to 700 C (1,100 to 1,300 F). Nues ardentes are exceedingly destructive, killing all living things in their paths. In some volcanic eruptions, the violent expansion of gas shreds the escaping magma into small, discrete particles. Both these masses of incandescent particles and the spectacular convoluting clouds of dust that rise above them actively liberate more gas. This series of expanding gas envelopes accounts for the nearly frictionless character of the flow as well as its great mobility and destructive power. Most nues ardentes occur in the Circum-Pacific region known as the Ring of Fire, but they may also occur in volcanic eruptions elsewhere. In 1902 the cloud of incandescent ash accompanying a glowing avalanche swept down on the city of St. Pierre, at the foot of Mount Pele in the West Indies, killing all but two of a population of about 30,000 persons.