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From: Jim Moore <jmoore@xxxxxxxx>
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In early October,1965 when I arrived in Manila to study the eruption of
Taal Volcano, I joined forces with Larry Andrews, then with the USGS, working
with the AID mission in Manila. He had witnessed the paryoxysmal
phreatomagmatic phase of the eruption from the district of San Lorenzo in
Manila at 0515 to 0730 September 28, 1965. His vantage point was 62 km north of
the eruptive center, which was on Volcano Island in the caldera lake of Taal
Volcano.
He gave me a sketch of his observations at that time, which has recently
come to light, and for which I did not then realize the significance. The
sketch shows a massive, knobby-textured, cylindrical eruptive column colored
pink from the dawn that was constantly sparkling from lightning. The column
extended upward 13 degrees above the horizon giving it a height of 14 km.
Diameter of the column was roughly 5 km. Above the column was a massive white
canopy with a wispy, feathery outer edge, above which was unaffected blue sky.
The top of the canopy was 30 degrees above the horizon, and the horizontal
width of the canopy exceeded 50 degrees.
I now realize that this was a giant umbrella cloud of the type produced at
Mount St Helens in 1980, fed by a column of heated air rising, not just from
the site of the explosions, but from the entire area covered by the widespread
hot base surges that spread out on the ground away from the explosion center.
I would be most interested in the observations of others who witnessed this
1965 Taal umbrella cloud and may possibly have taken photographs of it.
Photography would be a challenge because of the broad area of sky covered. At
Mount St Helens mosaicing of up to a dozen individual photographs was necessary
to image the entire cloud. In the intervening 42 years I have lost contact with
Larry Andrews and would be interested in his whereabouts.
Moore, J. G., Nakamura, Kazuaki, Alcaraz, Arturo, 1966, The 1965 eruption
of Taal Volcano: Science, v. 152, no. 3713, p. 955-960. Moore, J. G.,
1967, Base surge in recent volcanic eruptions: Bulletin Volcanologique, v. 30,
p. 337-363. Sparks, R. S. J.; J. G. Moore; C. J. Rice, 1986, The initial
giant umbrella cloud of the May 18th, 1980, explosive eruption of Mount St.
Helens: Journal of Volcanology and Geothermal Research, v. 28, p. 257-274.
Sincerely,
Jim Moore <jmoore@xxxxxxxx>
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