EOS Volcanology Logo Mount Pinatubo, Philippines

Slide set compiled by Rick Holasek, University of Hawaii
PINATUBO ERUPTION CLOUD, JUNE 15, 1991
Rick Holasek gratefully acknowledges the assistance of Fred Prata and CSIRO (Commonwealth Scientific and Industrial Research Organisation) in Melbourne Australia for help obtaining the GMS data.

These are a part of Rick Holasek's Ph.D. thesis, and some of it is in press in the paper by S. Self, J.-X. Zhao, R.E. Holasek, R.C. Torres, and A.J. King, The atmospheric impact of the 1991 Mount Pinatubo Eruption, part of a USGS Professional Paper edited by R.S. Punongbayan and C.G. Newhall, The 1991-1992 eruptions of Mount Pinatubo, Philippines.

Definitions

Column: Vertically rising volcanic ash and gas.

Plume: Horizontally moving volcanic ash and gas.

GMS Visible Images (0.5-0.75 micrometers wavelength, 1.25 km spatial resolution)

1331 Philippine Local Time (244K image size)
This image shows the beginning of the 3 hour long climactic eruption. The overshooting plume top in the center casts a shadow onto the main plume. The yellow X is the approximate location of the vent.

1431 Philippine Local Time (253K image size)
This image shows the climactic eruption approximately 1 1/4 hours after it started. The overshooting plume top in the center casts a shadow onto the main plume. The yellow X is the approximate location of the vent.

1531 Philippine Local Time (241K image size)
This image shows the climactic eruption approximately 2 1/4 hours after it started. The overshooting plume top in the center casts a shadow onto the main plume. Note the westward direction of the wind carrying ash at the altitude of the overshooting plume top, in contrast to the SW movement of the prevailing winds lower in the plume, where the majority of the wind-blown ash is being carried by the maximum atmospheric wind speeds at the tropopause. The yellow X is the approximate location of the vent.

1631 Philippine Local Time (223K image size)
This image shows the climactic eruption approximately 3 1/4 hours after it started. The overshooting plume top in the center casts a shadow onto the main plume. Note the westward direction of the wind carrying ash at the altitude of the overshooting plume top, in contrast to the SW movement of the prevailing winds lower in the plume, where the majority of the wind-blown ash is being carried by the maximum atmospheric wind speeds at the tropopause. The yellow X is the approximate location of the vent.

AVHRR Thermal Infrared Images (10.3-11.3 microns wavelength, 1.1 km spatial resolution)

1834 Philippine Local Time: 2D contour plot (134K image size)
This shows the different temperature levels within the giant umbrella plume. The temperature scale is in the lower right hand corner of the image. Temperature increases towards the center of the plume because it is getting higher in the stratosphere and therefore warmer. Comparisons of plume-top temperatures with ancillary data on atmospheric temperatures indicates the plume reached a maximum altitude of 34 km in this image. The cold region at the rising center of the column is due to plume undercooling. The buoyantly rising column overshot its level of neutral buoyancy and became undercooled due to rapid decompression. The black + is the location of the vent.

1834 Philippine Local Time: 3D plot (28K image size)
This three-dimensional representation shows the plume dimensions as rows and columns on the y and x axis, respectively. The z-axis shows the relative temperature in Digital Numbers (DN). Higher values are warmer (i.e., red) and lower values are colder (i.e., blue). Note the hot thermal "spike" in the center of the plume and the trailing green ridge. This is due to the great altitude reached by the overshooting central portion of the plume reaching high into the stratosphere (35-40 km) and warming significantly as a result. The trailing green ridge is the downwind ash blowing off the overshooting plume top at a high stratospheric level (ash shown in the GMS visible images above). The temperature of the ambient stratosphere exhibits a upwardly warming trend, and therefore the plume gets warmer as it reaches greater altitudes.

GMS Thermal Infrared Images (10.5-12.5 microns wavelength, 5 km spatial resolution)


Series of four images showing the different temperature levels of the plume-top as different color intervals. The color bar in the lower right hand corner delineates the different temperature levels. The red X shows the approximate location of the vent. Maximum altitude determined from comparing the plume-top temperature with ancillary data on atmospheric temperatures allowed us to determine a maximum altitude of 37 km at 1531 Philippine Local Time.

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