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Mount Pinatubo from the space shuttle
| STS046-075-79A Mount Pinatubo, Luzon, Philippines
August 1992 Mount Pinatubo is located on the island of Luzon,
approximately 75 miles (120 kilometers) northwest of Manila. Part of Subic Bay is visible
southwest of the volcano. Mount Pinatubo’s eruption in June 1991 is the largest
volcanic eruption of the 20th century. The grayish-tan, tentacle-like ash, mud, and debris
flows emanate from the nonvegetated blast zone around the volcano crater (center of
photograph). Heavy seasonal rains mobilize these volcanic ash flows (lahars) and cause
massive floods and destruction of bridges, roads, towns, and cultivated land. The
photograph shows new lahar deposits in many river valleys. The redistribution of lahars
and the impact on the surrounding countryside continue because the amount and duration of
precipitation combined with continued minor eruptions of the volcano can cause new
cascading into areas previously unaffected. (Photo and caption courtesy of NASA). |
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Click on image for enlarged view. |
Photomicrographs
of inclusions within phenocrysts of
Mount Pinatubo dacite by Professor
Jill Pasteris.
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Rounded-corner, square inclusions of glass in quartz showing different numbers and sizes of bubbles and different bubble:glass ratios. These are inclusions of trapped melt. Some of the bubbles are due to contraction of the melt during cooling. Some bubbles contain carbon dioxide and are inferred to represent trapping of a volatile phase that coexisted with the melt. |
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One-phase euhedral vapor inclusions (bottom left) coexisting with large, multi-phase aqueous inclusion (top; smaller, similar inclusions on right) in quartz. The latter inclusion is dominated by a vapor bubble. Among the visible solid phases, the lower-relief grain is isotropic and believed to be halite. Raman spectroscopy shows that the minute, colorless grains at the top apex of the inclusion are anhydrite. |
