Brian Dunbar
Headquarters, Washington, D.C.                                                                            
June 25, 1991
(Phone:  202/453-1547)

Delores Beasley
Goddard Space Flight Center, Greenbelt, Md.
(Phone:  301/286-2806)


RELEASE:  91-96

NASA TRACKS 4800-MILE VOLCANIC CLOUD FROM MOUNT PINATUBO


   Preliminary data estimates from a NASA satellite indicate a 
4,800-mile-long cloud of sulfur dioxide has spread across the 
tropical Northern Hemisphere from the major eruption of Mount 
Pinatubo volcano in the Philippines.  Research by Dr. Arlin 
Krueger, an atmospheric scientist at NASA's  Goddard Space Flight 
Center, Greenbelt, Md., indicates the cloud has drifted 4,800 
miles since the June 16, 1991, eruption. 

   The data was obtained from NASA's Total Ozone Mapping 
Spectrometer (TOMS), an instrument on the NIMBUS-7 satellite that 
measures ozone levels and monitors sulfur dioxide emissions.  
TOMS's mapping capability makes it possible to observe major 
volcanic eruptions, then track the plumes and measure the sulfur 
dioxide output during eruptions.  In the atmosphere, the gas 
reacts with water to form a sulfuric acid aerosol.

   Sulfur dioxide is a toxic gas known best as a major cause of 
air pollution.  Volcanic aerosols smaller than those produced by 
Pinatubo have been shown to have small, but measurable effects on 
regional climate.  The effects of the Pinatubo cloud will be 
important not only in assessing the impact volcanoes can have on 
climate, but in testing and modifying climate models as well.

   "What people can expect this fall are rosy sunsets as a 
result of aerosol particles produced from the cloud," Krueger 
said.  "There also is a possibility that the cloud will reflect 
back into space some of the sunlight that would have reached the 
ground, resulting is a small change in the heat balance of the 
Earth," he added.

   In terms of sulfur dioxide emissions, the Mount Pinatubo 
eruption may be two times larger than the eruption of El Chichon 
volcano in southern Mexico in April 1982, making Mount Pinatubo 
possibly the largest eruption this century.

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   The TOMS has monitored and measured ozone levels since 1978.  
Another TOMS is scheduled to be launched on a Soviet Meteor-3 
satellite on Aug. 15, 1991.  The TOMS program is managed by 
Goddard Space Flight Center for NASA's Office of Space Science 
and Applications, Washington, D.C.

                             -end-

Note to editors:  A NASA satellite image showing the cloud 
spreading across the Indian Ocean is available to news media 
representatives from the NASA Headquarters Audio-Visual Branch at 
202/453-8373.