THE GRAND ERUPTION OF VESUVIUS IN 1906^ 



WILLIAM HERBERT HOBBS 



Historical. — From the writings of Plutarch and Strabo we know 

 that previous to the Christian era where now is the complex cone 

 of Vesuvius, with its Atrium and Somma, the latter alone existed, 

 though in the form of a complete ring. This Strabo believed to 

 be a volcanic crater, though extinct. From the time of the earliest 

 Greek' colonization no records have been preserved of any eruption in 

 this crater previous to the eventful year of 79 a. d. ; though attention 

 has been drawn to the fact that wall-paintings recovered from the 

 buried cities of Pompei and Herculaneum represent the Somma 

 of those days with a somewhat broken wall as though from an erup- 

 tion. The careful studies of Johnston-Lavis have shown, however, 

 that in the composition and structure of Somma there is the record 

 of no less than fourteen periods of eruption, and of two long intervals 

 of repose not unlike that which immediately preceded the Christian 

 era.^ 



The eruption in the year 79, the greatest of Vesuvius within his- 

 toric times, was of the explosive type, producing no streams of 

 lava, but supplying such a vast quantity of lapilli and ash that, 

 carried by the tramontana then blowing, it was distributed over the 

 cities at the southern base of the mountain and along the slopes of 

 the Sorrentine peninsula. Pompei was covered in places to a depth 

 of 25-30 feet by this material; while the populous city of Hercu- 

 laneum, situated at the bottom of a steep slope, was overtaken by 

 a flood of mud and ash and buried beneath 60 feet of debris, now 

 augmented by lava streams from later eruptions. The vast quantity 

 of ejected material transferred the coast line from the former port 

 of Pompei to near its present position, reduced the ancient crater 



1 This article was dispatched from Rome a fortnight after the eruption. Various 

 causes have prevented its earlier publication. 



2 H. J. Johnston-Lavis, Eruptive Phenomena and Geology of Monte Somma and 

 Vesuvius in Explanation of the Great Geological Map of That Volcano (London, 1891; 

 pp. 21). 



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