of the Guzco Valley, Peru. 



91 



Huaccoto. 



The village of Huaccoto lies at the base of a small volcano. 

 Even at a distance this irregularly shaped ragged mound of 

 bare black rock 400 feet in height presents a striking contrast 

 to the softly molded grass-coated hills and swamp lands which 

 surround it. Near at hand the igneous mass is seen to consist 

 of five knobs separated by basin-like depressions within which 

 drainage is poorly developed. 'No crater is visible; the lava 

 appears to have emerged intermittently from several vents, 



Fig. 41. 



Fig. 41. Inca wall, Cuzco, built of augite diorite porphyry. 



making its way to the branched valley of the Huaccoto. The 

 longest continuous flow extends for about half a mile in a 

 southerly direction and terminates in a broken wall 10 to 15 

 feet in height. The original rough surface of the scoriaceous 

 lava has been greatly modified by the action of frost. Details 

 of vents, ropy structures, and caves are in large part replaced 

 by a superficial cover of broken blocks tilted at various angles. 

 The unweathered lava is light gray in tone, but weathering 

 produces a uniform color of rich red-brown. The rock varies 

 widely in texture. In some places flow structures are well 



