TEKTITES AND THE LOST PLANET — STAIR 227 



FLIGHT OF THE TEKTITES 



New, how do wc get the millions of small glass tektites from the 

 debris of the lost meteoric planet? Why not a few large chunks of 

 glass? Well, glass is a fragile article, especially when not well an- 

 nealed. It readily breaks upon mechanical or thermal shock. Take, 

 for example, a chunk of such material traveling at 40 to 50 miles per 

 second, the usual speed of many meteors. When it hits the earth's 

 atmosphere an immense amount of heat is developed at its surface. 

 The glass suffers both a terrific thermal and mechanical shock. Wliat 

 happens? It necessarily flies apart and is scattered in many small 

 pieces (Hubbard, Krumrine, and Stair, MS.) over a wide area, usually 

 elliptical in shape. The sizes of the many small pieces depend upon 

 the coefficient of expansion, the degree of annealing, and other phys- 

 ical properties of the material. Indeed, tektites having variations in 

 composition are found to vary in size in general accordance with their 

 physical characteristics. For example, Libyan Desert glass may be 

 found in pieces up to 10 pounds, while a moldavite, having an inter- 

 mediate coefficient of expansion, may weigh up to a pound or two, but a 

 tektite of relatively high temperature coefficient of expansion, for ex- 

 ample an australite or rizalite, is found only in very small pieces us- 

 ually weighing not more than an ounce or two. 



A study of other physical characteristics of the various tektites re- 

 covered also supports the above deductions. Striae, strain patterns, 

 and inhomogeneities indicate that the small pieces were once a part of 

 a larger body, since there is a lack of any appreciable distortions near 

 the surfaces. Plates 3 and 4 show this characteristic of a number of 

 the tektites. This rules out the formation of these glass specimens 

 by a fusion of meteoric material while passing near the sun in their 

 orbit before landing on the earth. The time of flight through the 

 earth's atmosphere is too short for the conduction of sufficient heat 

 to melt or soften the specimen deeper than a surface film which, for 

 the greater part, is swept away as it is formed. Only in the case of 

 some of the australites (whose prehistoric fall was geologically re- 

 cent) does any evidence remain to show the two distinct phases (Fen- 

 ner, 1949) in the formation of the glass specimen: the central core 

 of glass whose structure indicates a more or less annealed condition 

 indicating that the glass cooled slowly, and an outer surface having 

 high strain and other characteristics indicative of having undergone 

 softening at a later stage. All traces of double melting of all the other 

 tektites, which fell during various earlier ages, have long since been 

 eroded away. As noted above, and shown in plate 1, figure 1, an apron 

 is often left on australite specimens that apparently did not rotate 

 while in flight. Those that rotate may be expected to assume one of 

 the natural forms such as spheres, ovals, buttons, dumbbells, or the 



