Tarpeian Rock

“ Tarpeian Rock " of Tananarivo. From its summit were hurled all those who had the misfortune to incur the wrath of the sovereign. On the west side the slopes are too steep to afford space for the erection of many structures ; hence the dwellings are chiefly grouped on the gentler incline of the eastern side of the hill, where all are di ”

“ Tarawera itself towers above the lake, grim and dark and ominous; a mountain hot yet tamed by any means, and still hot, though not molten, in the interior of the cone.
On the shores of the lake, as the launch carries us past, can be seen, at one spot, the whitened bones of some of the natives who perished in the eruption. The name and titles of one, who was a great chief, are painted on a rock that overhangs the shore. ”

“ Trevorrick River was but a little stream to have fretted so deep a cleft between the hills as that which sloped from the main road of Tregols parish to the sea. From the source to the engulfing sands was barely a mile, and the twinkling waters, if full and fierce in winter, showed a summer fear of their own broad stepping-stones. Nevertheless the sharp declivities, the juttings of rock, even the shelves and crags and walls of Dark Head, had been formed by the gnawing of this tiny but persistent flow. ”

“ A gleaming speck of light flamed on the mirror's polished surface as it caught the sun, danced on fern and bush and boulder as I raised the glass and then, as I steadied it, came tremulously to rest on the topmost pinnacle of that terraced rock which Garth and I had climbed on the previous afternoon.
From where I stood I could see the edges of the three shelves which had been cut by some forgotten generation of cave-dwellers out of the friable volcanic rock. The speck of light trembled on the crag on a level with the topmost terrace. ”

“ If the foregoing views of the origin of trap-dikes in widely extended granitic regions far from rocks of any other formation, be admitted as probable, we may further admit, in the case of a great body of plutonic rock, being impelled by repeated movements into the axis of a mountain-chain, that its more liquid constituent parts might drain into deep and unseen abysses; afterwards, perhaps, to be brought to the surface under the form, either of injected masses of greenstone and augitic porphyry, or of basaltic eruptions. ”

“ From the north and east the massif of Tarrouaji appears a great jumble of hills of no great height, which do not die out at the plain’s edge with the impressive strength that may be found in great mountain slopes or towering cliffs, but rather do they tail away in broken diminishing lines to outlying plains, where little straggling hills of rock are seen as far as the eye can penetrate. ”

“ Such masses are termed trappean agglomerate and trappean breccia. At other times, however, the ejectamenta give evidence of having been arranged by the action of water, the materials having been sifted and spread out in more or less regular layers. What were formerly rude breccias and agglomerates of angular stones now become trappean conglomerates—the stones having been rounded and water-worn—while the fine ingredients, the grit, and sand, and mud, form the rock called trap tuff. Fragmental rocks are often quite indurated—the matrix being as hard as the included stones. ”

“ The eastern arm of the lake formed the outlet to the Tarawera river—the Awa-o-te Atua, or "river of the gods;" beyond the grand volcanic cone of Putauaki rose to a height of over 2000 feet, while right in front of our course the majestic outline of Mount Tarawera towered in the form of a colossal, truncated cone, with steep, sloping sides, tinted with red oxide of iron and shining obsidian, which made it look as if it were just cooling from the terrific heat of volcanic fires. ”

“ Resting upon and against the granite of the Wet Mountain range and its higher foothills, and extending down into the valley beyond the southern line of the belt, lies an enormous deposit of porphyry, or trachyte, a volcanic rock poured out and consolidated during the tertiary period. Its width is at least five miles, and its length is probably fifteen or twenty. Extending into the trachyte formation from the southwest, and following its general direction, is a tongue-shaped mass of granite about three-fourths of a mile wide and at least seven or eight miles long. ”

“ Upon climbing on the summit of a high conical hill I further discovered that the crater had an elongated shape, the longest diameter being from north to south, the southern and lower part being overlapped by a voluminous flow of lava which also covered a great part of the mountain slope. Strange monoliths were numerous, among the many fantastically shaped rocks, and also boulders lying about at all angles. One like a huge table rested on the top of another, upon which it had fallen with great force, as could be seen by the vertical splitting of the rock underneath. ”

“ Obbe, Harris, 7th July 1877.
This is written out on the hill-side—I will tell you why presently. Yesterday we walked from Tarbert, twenty-three miles, by a wild and lonely track-road, through a desolate and dreary region—nothing but bare rock, and a little heather and grass growing in rocks and crevices. It was all very interesting to me, however, as every square yard of rock was marked and scored and smoothed by the great ice-sheet that flowed out from the mainland. We took our time by the way, making notes and sketches. Every now and then we passed standing stones and ruins of Picts houses. ”

“ The fundamental rock is everywhere of a pale colour, generally compact, and of a feldspathic nature. In the S.E. portion of the island, where the highest land is situated, well characterised trachyte, and other congenerous rocks of that varying family, occur. Nearly the entire circumference is covered up by black and rugged streams of basaltic lava, with here and there a hill or single point of rock (one of which near the sea-coast, north of the Fort, is only two or three yards across) of the trachyte still remaining exposed. ”

“ It consists of nine separate little streams of lava piled upon each other; and of an irregular pinnacle, about fifteen feet high, of reddish-brown, vesicular basalt, abounding with large crystals of glassy albite, and with fused augite. This pinnacle, and some adjoining paps of rock on the beach, represent the axis of the crater. The streams of lava can be followed up a little ravine, at right angles to the coast, for between ten and fifteen yards, where they are hidden by detritus: along the beach they are visible for nearly eighty yards, and I do not believe that they extend much further. ”

“ Its steep ravines, which deepen as they approach the sea, recall to the southern voyager the ice-worn islands of the high latitudes. It seems improbable that these deep ravines which penetrate the hard volcanic rock, on their short course to the sea, could have been caused by their scanty brooklets.
The bowlders scattered over the island are not in harmony with the weathering process, while the obliteration of its craters seems to point to a more rapid process of erosion than could be attributed to weathering. ”

“ The hands and arms particularly, after they had been roasted over the fire, looked too human for words.
On October 4th we climbed a steep and rocky hill, crossing on its summit another section of the rocky plateau, a regular dome of grey volcanic rock. Then, descending from this second tableland on its eastern side, we had to struggle and stumble through most rugged country, where I found an extinct circular crater some 50 ft. in diameter and 50 ft. deep, with a vent at an angle in its bottom going apparently to a great depth. Near that spot was also a strange giant natural gateway of rock. ”

“ I have been living on dried whale’s flesh and shell-fish for I don’t know how many months past, and I was beginning to feel the scurvy breaking out in me; but all’s right now; I’ve no fear.”
Mr D’Arcy wished to have a look at the rock before leaving it, so he and I, and one of the midshipmen, landed. Our idea of its being the extinct crater of a marine volcano was undoubtedly correct. ”

“ Near the Baths of Cauquenes, between two short parallel lines of elevation, where they are intersected by the valley, there is a small, though distinct volcanic district; the rock is a dark grey (andesitic) trachyte, which fuses into a greenish-grey bead, and is formed of long crystals of fractured glassy albite (judging from one measurement) mingled with well-formed crystals, often twin, of augite. The whole mass is vesicular, but the surface is darker coloured and much more vesicular than any other part. ”

“ It was, I believe, when the fires of the great lake volcano died out that the waters rose from the subterranean springs below, and overflowing the then more elevated crater, distributed the light pumice rock over the area of country which had a gradual fall then as now in the direction in which the extensive deposits of pumice are still to be found. ”

“ The latter class must always be later than the rocks which they traverse, for it is plain the rocks must have been in existence before trap-dykes and veins could be shot through them. Hence geologists are accustomed to speak of contemporaneous and subsequent trap-rocks: the one list including all the tufas, and those melted rocks which can be shown to have been erupted during the time when the limestones, sandstones, or shales around them - 240 - were forming; the other embracing all the dykes and veins along with those beds of melted rock which have been intruded between the strata. ”

“ To my eye, the crystallized structure of pure white silica as it fell in congealed waves, as it were, from the steaming cauldron above, [Pg 95] appeared too flat, and required height to add more effect to its grandeur, while the rugged mountain, which formed its background, as it rose above a vapoury cloud of steam, looked dwarfed and insignificant in comparison with the giant form of Mount Tarawera, which frowned in silent majesty from beneath its spiked crown, as if eager to annihilate everything that failed to come up to its own idea of ponderous beauty. ”

“ Nothing whatever grows upon the slope. It is as bare as the side of a volcanic crater. And just as difficult to walk over. The talus is added to at the top by the falling rock of the face-wall, and it (39) is losing at the bottom by the under blocks grinding away to stone and gravel. The flattening out at the bottom, the breaking up of the blocks, and the push-out of the mountain foot upon the plain is the second stage of the talus. In almost all the large valleys of the desert the depressed talus extends, sometimes miles in length, out from the foot of the mountain range. ”

“ No species of rock occurs more abundantly in the embedded pebbles of this ancient conglomerate than rocks of the trap family. We find in it trap-porphyries, greenstones, clinkstones, basalts, and amygdalolds, largely mingled with fragments of the granitic, clay-slate, and quartz rocks. The Plutonic agencies must have been active in the locality for periods amazingly protracted; and many of the masses protruded at a very early time seem identical in their composition with rocks of the trap family, which in other parts of the country we find referred to much later eras. ”

“ Besides, we wanted to inspect the crater, feeling sure the mountain was an extinct volcano, and so determined to ascend to the highest elevation first, and then continue our journey northward over the country beyond, or through the channel which offered a clear passage in the direction of our course. This chasm through which the river ran was sublime and terrible. A rent in that stupendous rock formation which seemed to dwarf and threaten the very foundations of the earth on which it rested. ”

“ TARPEIA.
WOE: lightly to part with one’s soul as the sea with its foam!
Woe to Tarpeia, Tarpeia, daughter of Rome!
Lo, now it was night, with the moon looking chill as she went:
It was morn when the innocent stranger strayed into the tent.
The hostile Sabini were pleased, as one meshing a bird;
She sang for them there in the ambush: they smiled as they heard.
Her sombre hair purpled in gleams, as she leaned to the light;
All day she had idled and feasted, and now it was night.{36}
The chief sat apart, heavy-browed, brooding elbow on knee ”

“ We proceeded by a circuitous and steep route about six miles, gradually ascending the mountain, which consisted entirely of an uniform porphyritic rock, broken every where into fragments and large blocks, and which in many places was so denuded of soil, as to render it a matter of astonishment how vegetation, and particularly that of the cane, should thrive so well. The far greater part of the whole island is made up of this porphyry, which by some systematicks would be considered as referable to the newest floëtz trap formation, and by others would be regarded only as a variety of lava. ”

“ On the opposite side of it were again big domes of lava in corrugated designs, also a gigantic circular crater. Many natural crucibles of iron rock, some cylindrical in shape, others oval, others formed not unlike Pompeian lamps—while others still were square or rectangular or lozenge-shaped—were to be seen in many spots on the moraine-like tails that extended southward, like the tentacles of an octopus, and in the heaps of much carbonized rock and solidified froth produced by what was once boiling rock. The mounds of froth were usually collected in depressions. ”

“ When a great flow of lava spreads out upon the surface, there is no internal lamination or stratification, and the resulting rock is usually classified as massive rather than stratified; but when a succession of flows occur, each individual flow forms a layer, and the series as a whole becomes stratiform.499 The successive flows are not usually coextensive. If the later flows of the closing stages of a period of vulcanism fail to reach as far as the earlier ones, a terraced or step-like aspect is given to the region, whence the name trap-rock (trappe, steps) is derived. ”