TOPOGRAPHY AND GENERAL GEOLOGY. 11 



RANSOME. 



TOPOGRAPHY. 



The mines are situated in a group of bare, rounded hills forming 

 part of the high plateau extending south westward from Pikes Peak, and 

 are only about 10 miles distant from that prominent landmark. The 

 elevations range from 9,000 to nearly 11,000 feet above sea, the highest 

 point in the district being Trachyte Mountain (10,863 feet). Bull 

 Hill and Bull Cliff are but slightly lower. The drainage is chiefly 

 southward toward the Arkansas River. The district contains two 

 important towns. Cripple Creek is situated on the northwest side of 

 the producing area, while Victor, 3 miles distant, lies on the south- 

 west edge of the same area. Two railroads connect the district with 

 Colorado Springs, the Colorado Midland circling around the north 

 side of Pikes Peak, while the Short Line descends to the valley along 

 the picturesque eastern slope of the same mountain. The Florence and 

 Cripple Creek Railroad runs southward to Florence in the Arkansas 

 Valley. An excellent system of electric-car lines connects the towns 

 with all the important mines. 



GENERAL GEOLOGY. 



FIRST GEOLOGICAL SURVEY OF THE DISTRICT. 



When Mr. Whitman Cross made his careful study of the geology of 

 the Cripple Creek district, ten years ago, mining had barely begun 

 and the various hills were not, as now, perforated by deep under- 

 ground workings. That his work has in general stood the test of 

 subsequent underground exploration and continues to be highly 

 regarded in the district is convincing proof of its high quality. . Later 

 workers, however they may modify or amplify his results, should 

 acknowledge their debt to the pioneer who first deciphered the 

 history of this volcanic district. The account of general geology, as 

 given by Cross, ma} 7 be very briefly summarized as follows: 



The Cripple Creek hills lie near the eastern border of an elevated 

 and much dissected plateau which slopes gently westward for 40 

 miles, from the southern end of the Colorado Range, dominated by 

 Pikes Peak, to the relatively low hills connecting the Mosquito and 

 Sangre de Cristo ranges. The prevailing rocks of this plateau are 

 granites, gneisses, and schists. The granites inclose masses of Algon- 

 kian quartzite and are therefore post-Archean. But they are older 

 than the only Cambrian sediments known in Colorado, and on the 

 Cripple Creek map have been indicated as Algonkian. During 

 Tertiary time volcanic eruptions broke through these ancient rocks at 

 several points and piled tuffs, breccias, and lavas upon the uneven 

 surface of the plateau. The eruptive rocks of the Cripple Creek 

 district are the products of one of the smaller isolated volcanic centers 



