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Updated: May 5, 2025
This eruption went on until 1870, and the quantity of scoriae vomited forth during its continuance welded three islets, which had hitherto been separate, to the principal island, of which they now form part. On entering the Bay of Santorin we see on every side banks of lava, beds of scoriae, and piles of cinders of a purplish-gray color rising in cliffs to a height of more than 1,312 feet.
SCORIAE and PUMICE may next be mentioned, as porous rocks produced by the action of gases on materials melted by volcanic heat. SCORIAE are usually of a reddish- brown and black colour, and are the cinders and slags of basaltic or augitic lavas.
They contain no pebbles, or sand, or scoriae, or angular pieces of imbedded stone, and no traces of organic bodies, and they are often as crystalline as granite, yet are divided into beds, corresponding in form and arrangement to those of sedimentary formations, and are therefore said to be stratified.
Although none of these French volcanoes have been in activity within the period of history or tradition, their forms are often very perfect. Some, however, have been compared to the mere skeletons of volcanoes, the rains and torrents having washed their sides, and removed all the loose sand and scoriae, leaving only the harder and more solid materials.
Considering the abundance of earthy lime near the summit of Red Hill, a volcanic cone six hundred feet in height, of subaerial growth, considering the intimate manner in which minute particles and large masses of scoriae are embedded in the masses of nearly pure lime, and on the other hand, the manner in which small kernels and streaks of the calcareous powder are included in solid pieces of the scoriae, considering, also, the similar occurrence of lime and scoriae within a stream of lava, also supposed, with good reason, to have been of modern subaerial origin, and to have flowed from a hill, where earthy lime also occurs: I think, considering these facts, there can be no doubt that the lime has been erupted, mingled with the molten lava.
I cannot figure it better than by asking you to imagine a gigantic mass of pumice-stone, somewhat flat on top, and shelving on all sides very gently to the water, lying afloat but steady on the sea. It was of the hue of pumice, and as clean as an egg-shell, without a grain of calcined dust or any appearance of scoriae that I could anywhere observe.
The chief part consists of red decomposing scoriae, associated with various kinds of tuff and yellow argillaceous beds, full of broken crystals, those of augite being particularly large. Here and there masses of highly cellular and amygdaloidal lavas protrude.
Murray sometimes read aloud descriptions of beautiful scenery, written now among the scoriae of Mauna Roa or Mauna Kea, and now from the pinnacle of Mount Ophir, whence, through waving forests of nutmeg and clove, flashed the blue waters of the Indian Ocean, or the silver ripples of Malacca; and, on such occasions, the orphan listened eagerly, entranced by the tropical luxuriance and grandeur of his imagery, by his gorgeous word- painting, which to her charmed ears seemed scarcely inferior to the wonderful pen-portraits of Ruskin.
By the name mechanical are designated beds of mud, sand, or pebbles produced by the action of running water, also accumulations of stones and scoriae thrown out by a volcano, which have fallen into their present place by the force of gravitation.
In such cases we may suppose the tuff to have resulted from showers of volcanic sand and scoriae, together with fragments of limestone, thrown out by a submarine explosion, similar to that which gave rise to Graham Island in 1831.
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