National Geographic : 1996 Nov
On Volcano Watch Steam and dark clouds of ash billow from a volcano near Rabaul, Papua New Guinea (right), as the space shuttle Discovery flies over head. The eruption began on Sep tember 19, 1994, spewing ash and pumice around Blanche Bay and blanketing the city in a layer one to three feet deep. A few hours after this photo was taken, heavy rains soaked the ash, collapsing all but a handful of buildings. An eruption in 1937 killed more than 500. This time, warn ings kept the death toll down to five. Scientists often ask astronauts to photograph volcanoes as part of NASA's Earth Observations Project. On June 15, 1991, Mount Pinatubo in the Philippines-55 miles northwest of Manila-exploded in one of this century's largest volcanic eruptions, killing some 700 people. Less than two months later, the shuttle Atlantis sailed above the dirtiest atmosphere any astronaut could recall (above), a veil of dust shrouding Earth. Most of it was in two layers, at roughly 100,000 feet. Below them, anvil shaped thunderstorm clouds just above 40,000 feet mark the top of the troposphere. The layers of dust in this photo took years to dissipate.