Washington — Submarine Eruptions of 1831 and 1891. 131 



Art. YIII. — The Submarine Eruptions of 1831 and 1891 

 near Pantelleria / by Henry S. Washington. 



Introduction. — Of the regions which are noteworthy for 

 submarine eruptions, that part of the Mediterranean between 

 Sicily and Tunis has become classic. In this broad, deep strait 

 lie the two wholly volcanic islands of Pantelleria and Linosa, 

 which undoubtedly began with submarine eruptions, but whose 

 volcanic activity seems now to be quite extinct, or almost so. 

 That the vulcanicity of the district is not yet at an end has been 

 manifested several times during the nineteenth century, in the 

 years 1831, 1815, 1846, 1863, and 1891, as well as possibly in 

 1801 and 1832. Of these the phenomena of the eruptions of 

 1831 and 1891 were noted by competent observers, and material 

 ejected by them has been preserved and studied. Specimens 

 of the lava from both of these came into my possession and 

 have been examined with the miscroscope and analyzed, in 

 connection with a study of the rocks of Pantelleria which is 

 being carried out for the Carnegie Institution. 



A map of the strait between Sicily and Tunis is given in 

 fig. 1, based on the British Admiralty Chart 'No. 2158A, with 

 a few additional data. The volcanic islands of Pantelleria, 

 Linosa, and Graham are in solid black, and the site of Foerst- 

 ner Volcano is represented by a straight line. The locations 

 of the submarine eruptions of 1845 and 1846 are shown by 

 small crosses. The site of the eruption of 1863, though 

 reported to have been at that of Graham Island, is uncertain, 

 and a note on the B. A. Chart No. 2127 indicates that it was 

 searched for at the Hecate Patch. The hundred fathom line 

 is marked by a dotted line, and two fifty fathom lines, inclos- 

 ing the Adventure Bank and a small bank to the west, are 

 marked by dots and dashes. Small " patches, " where the 

 depth is less than 20 fathoms and often less than 10, are shown 

 by small dotted areas. Outside the hundred-fathom line the 

 soundings on the chart are seldom more than 400 fathoms, 

 though two of 717 and 890 are marked between Pantelleria 

 and Malta. 



It will be seen that the volcanic eruptions in general have 

 originated in comparatively deep water and outside of the 

 shelves which fringe the coasts of Sicily and Tunis, on which lie 

 respectively the limestone islands of Malta, Gozo, Lampedusa, 

 and Lampione, remnants of the early bridge between Italy and 

 Africa, which were separated by faulting probably in Pliocene 

 time. The known volcanoes, therefore, occupy the site of this 

 fault, and the occurrence of the small, shallow " patches " in 

 the continuation of the deep water to the northwest is interest- 



