3 resultados para Volcanic ash
em Digital Commons - Montana Tech
Resumo:
Between the villages of Rocker and Silver Bow, in southwestern Montana, are found an interesting group of placers. Gold occurs in Tertiary gravel beds that are interstratified with beds of rhyolitic volcanic ash. With the aid of a plane table and open-sight alidade, a small portion of the lake-bed area near Rocker was mapped; all distances were paced, but numerous checks assure a fairly accurate map.
Resumo:
The rhyolite rocks in the vicinity of Big Butte present a very interesting, though complicated study. It seems that no extensive or conclusive work has ever been done upon these extrusives. I have found that the rhyolites present a very interesting problem, especially microscopically, and that no doubt an intensive study along these lines will solve the problems concerning age relations of different flows and origin of the magma that produced the material for emanations.
Resumo:
Discussion of subduction zones that are associated with volcanic arcs and major chemical exchanges between the Earth's surface and underlying mantle.