Recent earth movements in the vicinity of Greeley Page: 4 of 7
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September 13, 1967
Jack Shipman4 LRL-N, photographed the crater September 11 from various
altitudes. He found the lip outline to be elliptical with a maximum
diameter of about 180 ft. and minimum of about 140 ft. The depth it
estimated at 170 ft. More precise dimensions will be available in a
day or two from the aerial topographic survey by American Aerial.
A radiation survey was conducted by REECO RadSafe around the crater
on Friday, September 8. The monitors made measurements as close as
100 ft. from the crater lip but found no activity above background of
.02 mr/hr. Beta plus Gamma. Bill King of LRL-N reported that the
minimum field detectable with their counters was about .08 mr/hr.
Two idealized vertical sections through the Greeley chimney are shown
in Fig. 2; one before subsidence of Earth's surface and the other
after subsidence. These sections are based on data obtained from the
post-shot exploratory hole shown in the figure. Don Rawson estimates
the cavity radius to be 260 ft. based on analysis of temperature and
high intensity gamma radiation logs. Based on the rate at which the
water level rose in the post-shot hole, Don estimates the height of
the rubble column to be-+l,500 ft. A void with a minimum height of
300 ft.was deduced to have existed at the chimney apex.
Analysis of the rate of ascent of the water level in the Greeley
post-shot hole indicates that collapse probably occurred around
September 1. Birdwell engineers report no change in level between
September 5 and September 12. Also, the latest valid measurement
prior to September 5 was on August 15 when the level was 14 ft.
lower. Rate of rise before August 15 was about 1 ft./day. It is
assumed that the additional collapse effectively sealed the lower
portion of the hole.
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Boardman, C. Recent earth movements in the vicinity of Greeley, report, September 1, 1967; United States. (digital.library.unt.edu/ark:/67531/metadc691796/m1/4/: accessed October 16, 2018), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.