Volcanoes produce a wide variety of

Volcanoes produce a wide variety of potential hazards that can kill people and wildlife, as well as destroy property(Figure 9.39) Perhaps the greatest threats to life are pyroclastic flows. These hot mixtures of gas, ash, and pumice that sometimes exceed 800 C race down the flanks of volcanoes, giving people little chance to escape. Lahars, which can occur even when a volcano is quiet, are perhaps the next most dangerous volcanic hazard. These mix tures of volcanic debris and water can flow for tens of kilometers down steep volcanic slopes at speeds that may exceed 100 kilo- meters(60 miles) per hour. Lahars potential threat to many communities downstream from glacier-clad volcanoes such as Mount Rainier. Other potentially destructive mass- wasting events include the rapid collapse of the volcano's sum. mit or flank. Other obvious hazards include explosive eruptions that can endanger people and property hundreds of miles from a vol- cano(Figure 9.40). During the past 15 years, at least 80 com mercial jets have been damaged by inadvertently flying into clouds of volcanic ash. One of these was a near crash that occurred in 1989 when a Boeing 747, with more than 300 pas- sengers aboard, encountered an ash cloud from Alaska's Redoubt Volcano. All four engines stalled after they became clogged with ash. Fortunately, the engines were restarted at the last minute and the aircraft managed to land safely in Anchorage.