4.1 - ENVIRONMENTAL GEOLOGY
MOUNT ST. HELENS, 1980 - NORTH AMERICA'S ERUPTION OF THE CENTURY - Mt. St Helens, southwestern Washington, had not erupted since 1857, but on May 18, 1980, a directional blast killed 63 people and caused hundreds of millions of dollars in damage in just a few seconds. A series of earthquakes that began in March, 1980 finally resulted in a landslide that thinned the north side of the volcano and allowed the explosive release of gases, ash and debris. That eruption stripped and leveled the area away from the base for about 10 kilometers. Little magma reached the surface and the eruption is mostly exploding gases rock fragments, and ash. Ash fell for days, as far away as Montana, disrupting daily human activities, but early warnings by the U.S. Geological Survey and evacuations saved many lives. An eruption similar to that of Mt. St. Helens could strike other Cascade volcanoes.

4.2 - IN GREATER DEPTH
VOLCANOES AND FLYING - In 1989, a KLM Boeing 747 flew into the ash plume of Mount Redoubt in Alaska at an altitude of 26,000 feet (8,000 meters). The pilot tried to climb out of the plume by applying full power, but all four engines stopped and the plane fell to 13,000 feet (4,000 meters) before the engines could be restarted. Examination of the engines revealed a coating of glass produced by the melting and resolidifying of ash. Repairs to the plane cost $80 million. The eruption of Mount Pinatubo (Philippines) in 1991 produced a sulfuric acid aerosol that scratched the acrylic windows of planes throughout the northern hemisphere.

4.3 - ENVIRONMENTAL GEOLOGY
A TALE OF TWO VOLCANOES - LIVES LOST AND LIVES SAVED IN THE CARIBBEAN - In May 8, 1902, Mount Pelée on the island of Martinique produced a searing (temperature estimated at 700^oC) pyroclastic flow that incinerated the city, the port and killed at least 28,000 people, even though the authorities had claimed that there was no danger, and refused to allow evacuations. In July, 1995, the Soufriere Hills volcano on the island of Montserrat, began to erupt. Volcanologists from France, the U.K., and U.S., monitored the volcano and advised evacuation first of the southern part of the island ahead of an eruption that destroyed the capital city of Plymouth in June, 1997, and then the northern part of the island, which experienced major eruptions in August, 1997. Only 19 people were killed as a result of these eruptions on Montserrat.

4.4 - ENVIRONMENTAL GEOLOGY
AN ICELANDIC COMMUNITY BATTLES A VOLCANO AND WINS - In 1973, eruptions on the Vestmann Islands threatened Heimaey with ash and flows. The residents fought to save the harbor from advancing lava by spraying water on it with fire hoses. That tactic worked, and regular clearing of the ash preserved most of the town's buildings from collapse. The accumulated ash was used to extend the airport runway, and the cooling flows have been used since 1982 to produce steam from water introduced into ash beds overlying them that is collected for home heating.

4.1 - ASTROGEOLOGY
EXTRATERRESTRIAL VOLCANIC ACTIVITY- Shield volcanoes are common features on the surface of the Moon, Mercury, Venus and Mars. Extensive lava flows form the lunar maria and similar features cover the surface of the solid planets. Wrinkle ridges related to lava cooling and subsidence, and rilles, cracklike valleys of several kilometers length, are represented as well. The extraterrestrial volcanism seems to be inactive, except for possible molten lava lakes on Venus. Nearly half of Mars is covered by volcanic material, and at least 19 shield volcanoes. The largest is Olympus Mons, that is three times higher than Mount Everest, and wider than California. Jupiter's moon Io is the only object in the solar system other than earth with an active volcano. The 10 active Io volcanoes erupt sulfur, sulfur dioxide, and a sulfur-silicate mixture. Neptune's moon Triton may have a nitrogen erupting volcano.