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The manner in which the various kinds of porphyries and andesites have been injected one into the other, and in which the infinitely numerous dikes of various composition intersect each other, plainly show that the stratified crust has been stretched and yielded many times over the same points.

The total thickness of the volcanic flows in this locality is as much as 4000 feet." It is to these breccias we owe the volcanic appearances in the Truckee River Canyon, a few miles before reaching the Lake. There are several layers of the andesites breccias at the head of Bear Creek Canyon, above Deer Park Springs.

Piquillacta is a large mass, nearly five miles long and two miles wide, rising to a point of 2000 feet above the Huatanay and Vilcanota rivers, it has no streams, brooks, or springs. It is an isolated, extinct volcano surrounded by igneous rocks, lavas, andesites, and basalts.