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In this case the yielding mass, squeezed, but unable to overcome the resistance which it meets with in a vertical direction, may be gradually relieved by lateral folding. In describing the manner in which strata depart from their original horizontality, some technical terms, such as "dip" and "strike," "anticlinal" and "synclinal" line or axis, are used by geologists.
On the eastern slope, the strata in the upper part are regularly inclined at about 25 degrees to the east, so that the summit of this chain, neglecting small irregularities, forms a broad anticlinal axis. Owing to the amount of denudation which this chain has suffered, the outline of the gently inclined eastern flank scarcely offers the slightest indication of this synclinal axis.
And again, the rim of the general basin, where it is elevated, as for example on the southwestern portion, instead of being a ridge sculptured on the sides like a mountain range, is found to be composed of many short ranges, parallel to one another, and to the interior ranges, and so modeled as to resemble a row of convex lenses set on edge and half buried beneath a general surface, without manifesting any dependence upon synclinal or anticlinal axes a series of forms and relations that could have resulted only from the outflow of vast basin glaciers on their courses to the ocean.
I believe that dislocations on so grand a scale are extremely rare in volcanic districts. Although the space between the Barn and Flagstaff Hill presents a distinct anticlinal line extending north and south, and though most of the dikes range with much regularity in the same line, nevertheless, at only a mile due south of the ridge the strata lie undisturbed.
Should the heat be retained for a long period, the strata would be so uplifted as to form an anticlinal, or saddle-back, and then, should subsequent denudation take place, more ancient strata would be brought to view.
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