TABLE 841.— ELASTIC CONSTANTS OF ROCK* 



741 



P (pressure), and K, R. E (bulk, rigidity, and Young's moduli resp), are given in bars (1 bar 

 = 10° dynes/cm 2 ). V P and V* (compressional and distortional wave velocities respectively), are 

 in km/sec. a is Poisson's ratio and p is the density, p is in g/cm\ 



Dynamically determined elastic constants are surrounded by parentheses (single parenthesis 

 represents seismic data); the others are static determinations. Italicized figures are calculated. 

 In places where insufficient data were present to complete the calculations, figures in square 

 brackets have been assumed. In the "P" column m.s. denotes mean stress. 



The basis of this table includes data of L. H. Adams and Williamson, F. D. Adams and Coker, 

 Bridgman and others. 



* Compiled by R. W. Goranson. 



TABLE 842.— AGE OF EARTH, MOON, AND STRATA 



The age of the earth is probably from (1.3 to 3) X 10 B years (radioactive data). Its 

 liquefaction was probably complete within 5,000 years, solidification within 15,000 years 

 from start. The age of the earth's crust may be taken as roughly 2,000 million years. 



Ages of geologic strata 



Late Oligocene 



" Cretaceous (?) 

 Permian-Carboniferous 

 Permian to Devonian.. 



37,000,000 yr 



59,000,000 " 



204,000,000 " 



239,000,000 to 



374,000,000 yr 



Late pre-Cambrian (?). 

 Upper pre-Cambrian . . . 

 Middle pre-Cambrian . . 



Lower pre-Cambrian . . . 



587,000,000 yr 



640,000,000 " 



987,000,000 to 



1,087,000,000 yr 



1,800,000,000 " 



SMITHSONIAN PHYSICAL TABLES 



