South Dakota School of Mines 61 



with the throats of vigorous volcanoes was from time to time 

 hurled high above the surface. Here favorable winds, catching 

 up the finely divided fragments, bore them far to the eastward 

 and there gently dropped them as thin widespread ashen blank- 

 ets to become an integral and interesting portion of the general 

 badland deposits. Subsequent to the Miocene the history of the 

 badland formations of the Black Hills region is largely one of 

 rapid weathering and vigorous erosion. 



PHYSIOGRAPHIC DEVELOPMENT 



The badlands of the Black Hills region are the result of 

 erosion, controlled in part by climatic conditions and in part 

 by the stratigraphic and lithologic nature of the deposits. There 

 is a too frequent lack of appreciation of the work of common 

 disintegrating and carrying agents and many an individual 

 speculates upon the mighty upheavals and the terrible volcanic 

 forces that to him have produced the wonderful ruggedness of 

 the badlands, when the real work, so far at least as immediate 

 topography is concerned, wholly apart from the forces of vul- 

 canism, have been performed under a kindly sun and through 

 benevolent combination by ordinary winds and frosts and rains, 

 and to a lesser degree by plants and animals. What the 

 earliest beginings may have been is not known. Suffice it 

 to say that then, as now, the sun shone, the winds blew, and the 

 rains came, and such irregularities as may have existed in- 

 fluenced in some degree the earliest run off. Season by season 

 the elements weakened the uplifted sediments, and little by little 

 the growing streams etched their way into the yielding surface. 

 In time lateral tributaries pushed their way into the interstream 

 areas and these tributaries in turn developed smaller branches, 

 the series continuing with ever increasing complexity to the 

 delicate etching at the very top of the highest levels. All the 

 important streams, the Little Missouri, the Grand, the Moreau, 

 the Cheyenne, and the Belle Fourche, the Bad, and the White 

 rivers, give indications of an eventful history, but for this there 

 is little opportunity for discussion here. Cheyenne river and 

 White river are the chief factors today in the production and 

 continuation of the badland features, and of these, White 

 river clings most closely to its task. The Cheyenne has already 

 cleared its valley of the badland deposits except in the important 

 locality southeast of the Black Hills and in the western Pine 

 Ridge area beyond the headwaters of White river, and 



