GRASSHOPPER GLACIER OF MONTANA — GURNEY 309 



Even if not brought down by a storm, grasshoppers falling on the 

 snow or ice become inactive after a few hours and eventually die. 

 Satisfactory preservation depends upon low temperatures and espe- 

 cially upon the grasshoppers' becoming embedded in the snow or ice 

 before decomposition reaches an advanced state. It is likely that 

 certain grasshoppers reaching the glacier decompose and disintegrate 

 before freezing takes place, while others may be covered immediately 

 by snow and frozen so that a perfect "deep-freeze" effect occurs. 



AGE OF THE GRASSHOPPER DEPOSITS 



The question immediately arises as to the age of the lowest layers 

 of preserved grasshoppers. Unfortunately no reliable estimate is 

 available, though there are plans for making a study by the carbon-14 

 test, the most modern method available. This method is based on 

 the fact that carbon-14 decays at a known rate, and when the amount 

 of carbon-14 in a particular object is known, its age can be calculated 

 (see Kulp et al., 1952) ? 



Eoberts (1952) has briefly but concisely explained the test and 

 has discussed archeological materials that have been studied by this 

 method. 



In August 1951, Dr. Irving Friedman, of the United States Geo- 

 logical Survey, visited Grasshopper Glacier and collected grasshop- 

 per fragments from the vertical ice face for the purpose of carry- 

 ing out a carbon-14 test at the Institute for Nuclear Studies, Uni- 

 versity of Chicago. The sample proved, however, to be inadequate, 

 being less than the approximate 15 grams of dry weight required, and 

 so, on August 28-30, 1952, Dr. Friedman again visited the glacier, 

 with three associates, and obtained more grasshopper material.* 



Can it be that the ice at the bottom of Grasshopper Glacier dates 

 back to the Pleistocene period or soon thereafter, or is it likely to 

 be of much more recent origin? Though the eagerly awaited re- 

 sults of a carbon-14 test seem the most likely to give a definite answer, 

 the historical geology of the area and some clarification of factors re- 



*See further comment on p. 326. 



1 As an example of an age estimate arrived at by the carbon-14 method, Kulp et al. 

 (1951) report their results from various samples, including a fossil cedar log dredged 

 from a harbor in Bermuda. The log is considered representative of a former cedar forest 

 which now is covered by 20 to 50 feet of water and mud. From the test conducted at 

 Columbia University, the age was calculated at 11,500 (±700) years. The Importance 

 cf this particular age determination is that the tree containing the log presumably grew 

 In the same position, indicating that the ocean was then at a much lower level ; this in turn 

 correlated with the period when much of the earth's water was still in the form of a 

 glacial covering. On the basis of this and other confirmatory studies, the last main stage 

 of the Pleistocene Epoch or Great Ice Age is thought to have been about 11,000 years ago. 

 Kulp and his associates also ran a test on a large wood sample that had been found beneath 

 gravel of the Mendenhall Glacier, Alaska. The sample was apparently from trees that 

 had been passed over by the glacier, so that the layers of glacial deposits associated with 

 the wood at that location are likely to be of a comparable age. This sample yielded an 

 estimate of 1,790 years, with a possible variation of 250 years. 



