EOS Volcanology Logo EOS Volcanology Slide Set #1
SURFACE AND ATMOSPHERIC EFFECTS OF THE 1991 ERUPTION OF MT. PINATUBO, THE PHILIPPINES

SLIDE #1 (292K)
Air photo of Mt. Pinatubo prior to the onset of activity, early 1991. Slide courtesy of Steve Self, University of Hawaii.


SLIDE #2 (396K)
The Total Ozone Mapping Spectrometer (TOMS) on Nimbus 7 recorded the dispersal of the Pinatubo plume by tracking the sulfur dioxide released. Slides #2-4 show the location of the plume from the June 15th eruption on the three successive days. This image is for June 16, 1991. The concentration of sulfur dioxide is expressed in units of milli-atmosphere centimeters, which gives the total column abundance in the atmospheric column. Image supplied by Gregg Bluth and Arlin Krueger, NASA Goddard Space Flight Center.


SLIDE #3 (219K)
(TOMS image of the June 15th eruption plume, as seen on June 17. The red dot marks the location of Mt. Pinatubo. Image supplied by Gregg Bluth and Arlin Krueger, NASA Goddard Space Flight Center.


SLIDE #4 (363K)
(TOMS image of the June 15th eruption plume, as seen on June 18. The red dot marks the location of Mt. Pinatubo. Image supplied by Gregg Bluth and Arlin Krueger, NASA Goddard Space Flight Center.


SLIDE#5 GIF image (38K) or Postscript image (870K)
The Microwave Limb Sounder (MLS) experiment on the Upper Atmosphere Research Satellite (UARS) recorded the dispersal of sulfur dioxide from Pinatubo in a different manner than TOMS (Slides 2-4). MLS has a microwave antenna that is oriented 90 degrees to the orbital direction of UARS, and can be mechanically scanned in a vertical direction to produce a profile through the atmosphere. These data are for a layer at an altitude of 22 km, and show measurements made on September 21, October 2, October 16, and November 17, 1991. Image supplied by Joe Waters and Bill Read, Jet Propulsion Laboratory.


SLIDE #6 (195K)
The Space Shuttle astronauts observed the aerosols from Pinatubo whenever they viewed the limb of the Earth for more than a year after the eruption. Here the aerosol layer is seen above thunder clouds over South America about three weeks after the July 15th eruption. Photo taken from the space shuttle Atlantis on mission STS-43.


SLIDE #7 (242K)
The Stratospheric Aerosol and Gas Experiment II (SAGE II) has been collecting optical depth measurements of the atmosphere since 1985 by means of solar occultations at the Earth's limb. SAGE II has been used to study the amount and temporal distribution of stratospheric aerosols resulting from the Pinatubo eruption. The mapped data are stratospheric optical depth at a wavelength of 1.0 micrometer, constructed from individual SAGE II extinction profiles. This slide shows data collected before the Pinatubo eruption between April 15 and May 25, 1991. This scene is dominated by a near-background stratospheric optical depth, although there is a slight enhancement in the southern hemisphere as a result of the eruption of Kelut volcano in February, 1990. A comparison of these data with Slides #8 and #9 show the progressive effects of the eruption on the loading of the stratosphere. Image supplied by Pat McCormick, Langley Research Center.


SLIDE #8 (193K)
SAGE II map of the distribution of stratospheric aerosols from the Pinatubo eruption between June 14 and July 26, 1991 (i.e., the period of the major eruptions). This image shows the nearly two orders of magnitude increase in the optical depth observed in the tropics. In the northern latitudes, low-altitude transport permitted a small increase in the optical depth while the southern hemisphere remained quite clean. Compare with Slides #7 and #9. Image supplied by Pat McCormick, Langley Research Center.


SLIDE #9 (202K)
SAGE II map of the distribution of stratospheric aerosols from the Pinatubo eruption between February 13 and March 26, 1993 (i.e., 18 months after the eruptions). By this time, the optical depth is still highly perturbed compared to the preeruption atmosphere, but the hemispheric differences are mostly gone. Compare with Slides #7 and #8. Image supplied by Pat McCormick, Langley Research Center.


SLIDE #10 (256K)
Listing of the estimates of aerosol mass loading in the stratosphere by volcanic eruptions. Notice that Pinatubo produced the greatest loading over the entire period for which we have data. Table supplied by Pat McCormick, Langley Research Center.


SLIDE #11 (347K)
Air photo of the main crater and growing lava dome at Pinatubo after the eruptions. Photo taken in November, 1992, by Rick Holasek, University of Hawaii.


SLIDE #12 (302K)
Ground photo of the pyroclastic flows 2 km southwest of the Pinatubo vent. Rick Holasek is seen here measuring the temperature of some of the fumaroles on the still-hot pyroclastic flows. Maximum fumarole temperatures of 387 degrees C were measured 15 months after their emplacement. Photo by Steve Self, University of Hawaii.


SLIDE #13 (329K)
The effects of the mudflows generated by the remobilization of the Pinatubo ash deposits are dramatically illustrated by this slide and Slide #14, which show the same river channel before and after the deposition of a mud flow (also called a "lahar"). The key place to look at is the house in the bottom of the image. Photo by Ronnie Torres, University of Hawaii.


SLIDE #14 (279K)
Same view as Slide #13, except after the deposition of the lahar. Photo by Ronnie Torres, University of Hawaii.



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