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Updated: June 23, 2025
The great size and age of some of these trees indicate, the lapse of time between the eruption whose lavas or tuffs weathered to the soil on which they grew and the subsequent eruption which buried them beneath showers of stones and ashes.
Many of them cut all the inclined beds in the escarpment of Somma from top to bottom, others stop short before they ascend above halfway. In mineral composition they scarcely differ from the lavas of Somma, the rock consisting of a base of leucite and augite, through which large crystals of augite and some of leucite are scattered.
Since that day various eruptions have temporarily desolated portions of the territory, but only in very small fields have the ravages been irremediable. Where the ground was covered with dust, it has in most places been again tillable, and so rapid is the decay of the lavas that in a century after their flow has ceased vines can in most cases be planted on their surfaces.
The fragments consist usually of different varieties of scoriaceous and compact lavas; but other kinds of rock, such as granite or even fossiliferous limestones, may be intermixed; in short, any substance through which the expansive gases have forced their way.
This period was followed by other dilatations of the same veins, and the introduction of other sets of mineral deposits, as well as of pebbles of the basaltic lavas of Auvergne, derived from superficial alluviums, probably of Miocene or even Older Pliocene date.
Professor Judd says: "The most interesting fact with regard to the constitution of these Hungarian lavas, which in the central parts of their masses are often found to assume a very coarsely crystalline and almost granitic character, while their outer portions present a strikingly scoriaceous or slaggy appearance, remains to be noticed.
The Uspallata tuffs and great streams of submarine lavas, were probably intermediate in age between the cretaceo- oolitic and older tertiary formations, and we know from the buried trees that there was a great subsidence during their accumulation; but even in this case, the subsidence may not have been strictly contemporaneous with the great volcanic eruptions, for we must believe in at least one intercalated period of elevation, during which the ground was upraised on which the now buried trees grew.
The almost entire absence of associated grasses, which forms so remarkable a feature in the vegetation of this island, may perhaps be accounted for by the land having been aboriginally covered with forest-trees. The soil is volcanic; in several parts we passed over shaggy lavas, and craters could clearly be distinguished on several of the neighbouring hills.
At all three islands, deluges of more recent lavas have flowed from the centre of the island, towards and between the basaltic mountains; and at St. Helena the central platform has been filled up by them. All three islands have been raised in mass. At Mauritius the sea, within a late geological period, must have reached to the foot of the basaltic mountains, as it now does at St.
A bullock-cart, laden with pitch, came jolting down past us; and we observed that the lumps, when the fracture is fresh, have all a drawn-out look; that the very air-bubbles in them, which are often very numerous, are all drawn out likewise, long and oval, like the air-bubbles in some ductile lavas.
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