2G8 GEOLOGICAL EXCURSION TO THE ROCKY MOUNTAINS. 



THE APPALACHIAN REGION." 

 By <;. II. Williams. 



The first day's ride of the excursion is well calculated to give a clear 

 idea of the character of that regular mountain belt which bounds the 

 entire North American continent on its southeast side. The general 

 type of Appalachian structure is well known to all geologists, either 

 through the classic work of the brothers Rogers, 1 or from the summary 

 of their results given by Dana and others. The railroad course to be 



followed during the first day traverses the entire belt front east to 

 west along one of its narrowest, deepest, and most characteristic sec- 

 tions, i. e., that which lias been excavated by the Potomac River. 



The recent work of several geologists, but notably that of Mr. \V ,1 

 McGee, 6 has clearly demonstrated the divisibility of the mountain and 

 coastal portion of the eastern United States south of New York into 

 three topographically and geologically distinct provinces or zones. 

 Together they embrace nearly the entire sequence of geological forma- 

 tions, while at the same time the age, petrographieal character, ami 

 structure of each is widely different from that of the others. 



The most recent, as well as the most easterly, of these three zones is 

 called the Coastal plain. It varies greatly in width between New York 

 and Florida, but is throughout composed of Dearly unconsolidated 

 Mesozoic and Tertiary strata (clays, sands, and gravels), which dip 

 very gently seaward, and in this direction -row steadily younger 

 Over all, however, is spread a capping of Pleistocene gravel (< lolumbia) 

 ihe western edge of this Coastal plain may be regarded as approxi- 

 mately coincident with a line drawn from New York to Washington 

 and it is not improbable that a flexure or fault, still in process of 

 development along this line, separates it from the crystalline region 

 on the west. 7 ' s 



The next of the three provinces or zones in point of geological age 

 although no the one geographically contiguous to the Coastal plain?* 

 tin- Appalach.au .Mountain belt. These two are separated by the tin d 

 and much the most ancient zone, composed of highly crvstallme rocks 

 orsemicrystaUnie rocks, and known as the Piedmont piateau. ' 



The Appalachian Mountain BeU embraces nearly the entire sequence 

 oMaleozo,c strata. In the section to be traversed during daylight" 



World's Fair book «S v , 1 I ' *e 8 trata m colors, has been published in the 



