Volume 2

Principles of geology : being an inquiry how far the former changes of the earth's surface are referable to causes now in operation. / By Charles Lyell ...

  • Lyell, Charles, Sir, 1797-1875.
Date:
1834
Catalogue details

Licence: Public Domain Mark

Credit: Principles of geology : being an inquiry how far the former changes of the earth's surface are referable to causes now in operation. / By Charles Lyell ... Source: Wellcome Collection.

Provider: This material has been provided by King’s College London. The original may be consulted at King’s College London.

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    proportion, the ordinary elevation of the volcanic mass becomes ten thousand feet, and its greatest more than double that of the Himalaya mountains. It will im- mediately be granted that, among the older formations, no igneous rock of such colossal magnitude has yet been met with ; nay, it would be most difficult to point out a mass of ancient date distinctly referrible to a single eruption, which should even rival in volume the matter poured out from Skaptar Jokul in 1783. These considerations, however, cannot present serious objec- tions to geological theorists, for it is a received prin- ciple with them, that we ought always to assume the energies of natural forces to have been impaired and enfeebled, until tbe contrary can be shown ; and as we have hitherto investigated but a small part of the globe, evidence may hereafter be brought to light of the su- perior violence of single volcanic eruptions in remote ages. If proofs be still deficient, there is always a resource of which the geologist in Voltaire’s tale knew how to avail himself, Monsieur, on en decouvrira ! * Eruption of Jorullo in 1759.— As another example of the stupendous scale of modern volcanic eruptions, I may mention that of Jorullo in Mexico, in 1759. The great region to which this mountain belongs has already been described. The plain of Malpais forms part of an elevated platform, between two and three thousand feet above the level of the sea, and is bounded by hills composed of basalt, trachyte, and volcanic tuff, clearly indicating that the country had previously, though probably at a remote period, been the theatre of igneous action. From the era of the discovery of the New World to the middle of the last * L’Homme aux quarante ecus.