222 POPULAR SCIENCE MONTHLY. 



A GEOLOGICAL ROMANCE. 



By J. A. UDDEN. 



A WESTERN naturalist once said that the geology of Kansas 

 was monotonous. In one sense this remark is certainly justi- 

 fiable, and the same may be said about the geology of some of the 

 other States on the Western plains. The American continent is built 

 on a comprehensive plan, and many of its formations can be followed 

 for hundreds of miles without presenting much variation in general 

 appearance. Occasionally, however, some feature of special interest 

 crops out from the serene uniformity, and the very nature of its sur- 

 roundings then makes it appear all the more striking. Minor acci- 

 dents in the development of our extensive terranes sometimes stand 

 out in bold relief, as it were, from the monotonous background. In 

 their isolation from other details such features occasionally display 

 past events with unusual clearness. 



Such is the case with a deposit of volcanic ash which has been 

 discovered in the superficial strata on the plains.* It lies scattered 

 in great quantities in a number of localities in Nebraska, Kansas, 

 South Dakota, and Colorado, having been found in no less than 

 twenty counties in the first-mentioned State. It measures from two 

 to fourteen feet in thickness in different localities, and is mostly 

 found imbedded in yellow marl and clay, and has a somewhat striking 

 appearance in the field, due to its snowy whiteness and to the sharp- 

 ness of the plane which separates it from the underlying darker 

 materials. Many years before its real nature was known it had been 

 noticed and described by Western geologists. Prof. O. T. St. John 

 saw it many years ago in Kansas, where it appeared as " an exceed- 

 ingly fine, pure white siliceous material," forming a separate layer 

 of several feet, and set off by a sharp line from the buff clay-marl be- 

 low. His words describe its usual appearance in other places (see 

 Fig. 1). 



This ash occurs in several outcrops in McPherson County in the 

 central part of Kansas, where the writer had an opportunity to 

 study it somewhat in detail a few years ago. Some of the features 

 of the dust at this place reveal the conditions under which it was 

 formed with considerable distinctness, and the volcanic episode 

 which produced it appears strikingly different from the dull monot- 



* Dr. Samuel Augbey, Physical Geography of Nebraska, 1880. Prof. J. E. Todd, Sci- 

 ence, April 23, 1886, and January 8, 1897. E. H. Barbour, Publication No. V, Nebraska 

 Academy of Sciences. J. A. Udden, The American Geologist, June, 1891, and April, 1893. 

 R. D. Salisbury, Science, December 4, 1896. G. P. Merril, Proceedings of the United States 

 National Museum, 1885. 



