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.