OCR Text |
Show 307 base of the cone is coarsely vesicular and of a dark- brownish color, entirely dissimilar in appearance from the basaltin the neighboring mesas, which latter varies iroin reddish to dark brown, specked with light gray, and homogeneous in texture. To the eastward, the low, uneven platform drops down into the depression between the Gapulin and Sierra Grande, in which is gathered the drainage of the headwaters of the dry Cimarron. The lines of low basalt- capped bluffs on the west and northwest borders of the vega present at least two distinct benches, of which the lowest is about 75 feet in height, the other or highest ( that shown on the left of the Gapulin in the sketch) perhaps as high again above the vega. The lower one presents along its crest frequent abrupt outcrops, but in the higher bench the basalt forms a low uninterrupted wall, showing very irregular columnar structure, below which the dibris* strewn talus descends to the lower levels. There is also here observed a lower basaltic outcrop, which forms a third irregular bench, somewhat less than half the height of the next higher bench; but whether it represents a distinct deposit, independent of those appearing in the higher terraces, was not determined. Indeed, the thickness of the basaltic beds was in no place satisfactorily exhibited, though in places the upper one shows a solid outcrop of 20 to 30 feet without revealing the nature of the deposits upon which it rests. Nearly due north of the Vega Spring, overlooking the intervening basaltic beds above alluded to, another volcanic cone rises to view, which, though not so perfect as the Capulin, is yet unmistakable in its origin; the western rim is deeply broken down, showing the crater-depression, while the opposite wall still remains perfect, and is much like that of the Capulin. Perhaps not quite as Ligh as the latter cone, it rests upon a similar uneven upland eminence, and is grassed over to the summit. The formation of these high spreading bases seems to be directly attributable to the volcanoes themselves, and may have been built up in the early stages of the eruption, which terminated in the building- up of the conical elevations around their orifices. The Sierra Grande, like Laughlin's Peak, when seen from the west, presents a broad- based mass gradually culminating in a blunt or rounded summit, which attains an altitude of about 8,000 feet. Laughliu's Peak, however, viewed from the northwestward, shows a deep depression extending half- way from the summit to its broad base, and which has all the appearances of a crater, the northwestern rim of which has been demolished. The contour of both these mountains, as also that of the Eagletail, suggests their possible origin as centers of volcanic eruptioti; but they probably mark the sites of much larger and possibly older craters than the Capulin and others, which still retain their symmetrical form and undoubted character. Their conical shape would seem to indicate a different origin from that of the basaltic overflows, which distinction, in the case of the Capulin, is also quite manifest in the difference in the physical character of the igueous products ejected, and out of which the cone surrounding its crater was built up.. There would appear to be several distinct basaltic deposits in this region, as evidenced by the presence of at least three or four benches, or terraces, of different levels. As stated above, there are at least two such deposits, occupying comparatively low elevations, bordering the Capulin Vega; and probably a third and lowest bench, which latter, from the character of the material thrown out from the excavatious of some burrowing animal ( perhaps the prairie- dog) in the edge of the vega, apparently rests upon light, indurated, marly shales, probably |