. Elements of geology : a text-book for colleges and for the general reader. Geology. Fig. 83. -Section across Barren Island (after Mallett): s I, sea-level, show the supposed former condition. The dotted line is added to Comparison between a Volcanic Cone and an Exogenous Tree.—It is evident, then, that a cone of eruption grows by layers successively applied on the outside. Both in structure and growth it may, there- fore, be compared to an exogenous tree: 1. As the sap ascends through the center of the shoot and descends on the outside, forming layers of wood, one outside of the other, incre
. Elements of geology : a text-book for colleges and for the general reader. Geology. Fig. 83. -Section across Barren Island (after Mallett): s I, sea-level, show the supposed former condition. The dotted line is added to Comparison between a Volcanic Cone and an Exogenous Tree.—It is evident, then, that a cone of eruption grows by layers successively applied on the outside. Both in structure and growth it may, there- fore, be compared to an exogenous tree: 1. As the sap ascends through the center of the shoot and descends on the outside, forming layers of wood, one outside of the other, increasing every year the height and the diameter of the tree ; so in a volcano lava ascends through the center and pours over the outside, forming also successive layers, in- creasing both the diameter and the height. 2. As a cross-section of a tree shows concentric rings around (Fig. 84) a central pith, and is traversed by pith-rays ; so a cross-section of a volcano would show a central crater, with con- centric layers, traversed by radiating dikes. 3. As on the pith-rays, where they emerge upon the surface, arise buds, which grow in a man- ner similar to the trunk; so on the radiating dikes are formed monti-. Fig. 84. Medlicot and Blandford, Manual of Geology of India, p. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original LeConte, Joseph, 1823-1901. New York : D. Appleton and Co.
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Keywords: ., bookcentury1800, bookdecade1890, booksubjectgeology, bookyear1892
