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Show 200 GEOLOGY OF THE HIGH PLATEAUS. given by the first view. The surfaces of the fragments are not affected by weathering to any notable extent, and it is only by comparison with surfaces fractured by the hammer that we can find an assurance of an exceedingly slight impairment of its original freshness. No doubt this is largely due to the fact that this portion of the mass is not in the slightest degree vesicular. In other parts of the coulee highly vesicular fragments were encountered; but where I first approached it every stone was as compact as a dike. But even the vesicular specimens show so little weathering, that it is hard to believe that this eruption is as old as the discovery of America. Such appearances, however, may be very deceptive. I am not aware that there is any authentic record of a volcanic eruption within the present limits of the United States, though it is quite possible that a number of them have occurred since the conquest of Mexico by Cortez. In this region it may have easily escaped the chronicles of the Spanish priests, even if such a dire event had occurred only a hundred years ago, and two hundred years would have destroyed all reliable tradition of it among the Indians.* This basalt came from a vent situated about 3 miles southwest of Panquitch Lake, and from the same source flowed a considerable number of large streams all presenting the same appearance of recency. An attempt was made to reach the crater, but the climbing over the rough angular blocks piled up in the worst conceivable confusion proved to be so perilous, that after several misadventures it was abandoned. From surrounding eminences several overlooks were obtained, from which it was inferred that there are several vents clustered near each other, and from three of them at least there have been a number of eruptions. Nothing like a cinder-cone, however, was distinguishable. The lavas appear to have reached the surface and overflowed like water from a spring, spreading out immediately and deluging a broad surface around the orifice, and sending off into surrounding valleys and ravines deep rivers of molten rock. One flood rolled northeast towards Panquitch Lake, but came to rest before reaching it. A second flowed eastward down a broad ravine situated about 3 miles from the lake. The largest streams went to the southeast into * There ia said to be a tradition among the Mohave Indians that their ancestors were driven out of Central Arizona by volcanic eruptions, and though very recent basalts are found there, many circumstances combine to oppose such a tradition even if there be one. |