504 ALLEN DAVID HOLE 
3. The plateau north and south of the Wilson group, cut by 
deep canyons in which flow the San Miguel, and the East Dolores 
rivers and their tributaries. 
The highest point in the quadrangle is Mt. Wilson, near the 
western side, 14,250 feet above the sea; numerous peaks, however, 
in the eastern half rise above 13,500 feet, and ridges extend for 
miles with crests at an elevation greater than 13,000. The lowest 
point in the quadrangle is in the canyon of the San Miguel River, in 
the northwestern part, an elevation of 7,500 feet; but the plateau 
in which the canyon is cut has at most points an elevation of not 
less than 9,000 feet. 
The topographic features as they exist today in the quadrangle 
are the result of agencies which have been in operation from a 
remote period in the history of the earth to the present time. The 
earlier include all those forces and processes which culminated in 
the relative elevation of the land thousands of feet above the sea, 
the ejection of enormous quantities of lava and other volcanic 
material, and the dissection of this elevated and ejected material by 
erosion, until, at the opening of Pleistocene time, the mountains, 
plateaus, and main stream channels must have had positions rela- 
tively much the same as they have now. The details of the topog- 
raphy, however, are due to agencies which have operated within 
Pleistocene and recent times; chief among these agencies which 
have produced results more or less well marked are: (1) agents of 
weathering, including freezing and other changes in temperature; 
(2) running water; (3) lakes and ponds; (4) moving masses of snow 
and ice, not glacial; (5) landslides; (6) glaciers. 
GEOLOGICAL FORMATIONS 
Observations in regard to the geology and topography of areas 
within this quadrangle have been made by a number of scientists, 
including members of the Hayden Survey and representatives of 
the War Department of the United States, as well as many others; 
the first detailed work to cover the entire area, however, was that 
undertaken by Mr. Whitman Cross and his associates, the results 
of which were published by the United States Geological Survey in 
the Telluride Folio, in 1899, from which the summary given below 
is largely taken. 
