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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    upper part (only about two hundred feet high) emerged above the waters, so as to form an island. This cone must have been equal in size to one of the largest of the lateral volcanos on the flanks of Etna, and about half the height of the mountain Jorullo in Mexico, which was formed in the course of nine months, in 1759. In the centre of the new volcano a large cavity was kept open by gaseous discharges, which threw out scoria;; and fluid lava probably rose up in this cavity. It is not uncommon for small subsidiary craters to open near the summit of a cone, and one of these may have been formed in the case of Graham island ; a vent, per- haps, connected with the main channel of discharge which gave passage in that direction to elastic fluids, scoriae, and melted lava. It does not appear that, either from this duct, or from the principaTvent, there was any overflowing of lava; but melted rock may have flowed from the flanks or base of the cone (a common occurrence on land), and may have spread in a broad sheet over the bottom of the sea. No. 20. removed by the waves ; the strong lines represent the part of the volcano which is still under water. In the centre is a great column, or dike, of solid lava, two hun- dred feet in diameter, supposed to fill the space by