File:Etna - a history of the mountain and of its eruptions (1878) (14779250781).jpg

Identifier: etnahistoryofmou00rodw (find matches)
Title: Etna : a history of the mountain and of its eruptions
Year: 1878 (1870s)
Authors: Rodwell, G. F. (George Farrer), b. 1843 Cavagna Sangiuliani di Gualdana, Antonio, conte, 1843-1913, former owner. IU-R
Subjects: East Timor News Agency Volcanoes Volcanic soils Volcanic ash, tuff, etc
Publisher: London : C. Kegan Paul & Co.
Contributing Library: University of Illinois Urbana-Champaign
Digitizing Sponsor: University of Illinois Urbana-Champaign

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ofthe Norwich crag; and the oldest eruptions of Etnamust have taken place during the glacial period, butbefore the period of greatest cold in Northern Europe. Before visiting Etna, Lyell had been told by Dr.Buckland that in his opinion the Val del Bove was themost interesting part of Etna, accordingly he speciallyand minutely examined that part of the mountain.This vast valley is situated on the eastern flanks ofthe mountain, and it commences near the base of thecone, stretching for nearly five miles downwards. Itis a large oval basin formed in the side of themountain, and surrounded by vast precipices, some ofwhich at the head of the valley are between three andfour thousand feet in height. The surface is coveredwith lava of various dates, and several minor cones,notably those of 1852, are within its boundaries. Theabrupt precipices reveal the presence of a large numberof vertical dikes, radiating from a point within thevalley, some of them, according to Yon Walter- 121 $ir<\&
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o ;; r--o p. o£« O fl E^ ^ r/5 5.3 ■+f 11 o3 o oi 13 B « 122 ETNA. shausen, being of ancient greenstone. Other dikes otmore modern doleritic lava radiate from the presentcrater. From the slope of the beds in the Yal delBove, Lyell and Yon Waltershausen have independentlyinferred that there was once a second great centre oferuption in the Yal del Bove between the SierraGiannicola, and Zoccolaro (vide the Figure on p.117). The axis of eruption passing through thispoint Lyell calls the Axis of Trifoglietto; while hedistinguishes the present centre of eruption as the Axisof Mongibello. These centres probably existed simul-taneously, but were unequal as regards eruptive violence;the crater of Mongibello was the more active of the two,and eventually overwhelmed the crater of Trifogliettowith its products, by which means the whole mountainbecame a fairly symmetrical cone, having the crater ofMongibello at its apex (vide the Figures on pp. 119 and121). Subsequently the

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