THE VOLCANOES AND ROCKS OF PANTELLERIA 663 
represented by Monte Fosso del Russo, Monti Gibilé a and 3, 
Monte Gelfiser, Cuddia Randazzo, and others. The faults accord- 
ing to Foerstner, are the cause of, and are represented by, the 
various encircling scarps mentioned in describing the topography 
and certain coastal features. 
At the close of this period of dislocation the last of the pan- 
tellerite cones was formed, that of Monte Sant’ Elmo and Cuddia 
del Catt, after which the lava underwent a change in composition, 
“by subtraction of silicic acid.” The last phase of basaltic erup- 
tions began with an outburst on the northwest flank of Sant’ Elmo, 
and was continued in the small cones of basaltic scoriae and flows 
of basalt. 
Bergeat’s views.—The geological structure has also recently been 
briefly discussed by Bergeat,‘ who cites the mass of Montagna 
Grande as an example of Stawkuppen or plug domes, analogous to 
the spine of Mont Pelée. He adopts the views of Foerstner that 
the prominent scarps are due to faulting, and indicates on a map the 
traces of what he considers to be the chief fault-lines, as shown by 
volcanic cones, scarps, or other lineaments. He calls attention, 
however, to the fact that a depression would more naturally be 
supposed to follow the ejection of lavas on a large scale than the 
upheaval advocated by Foerstner, and would explain equally well 
the formation of Montagna Grande and the precipitous scarps. 
On his view the upthrust of Montagna Grande is supposed to be a 
differential one, due to subsidence of the encircling portion. Ber- 
geat considers that Monte Gibelé was the volcanic center for the 
whole mass of Montagna Grande and that the two were separated 
by a fault which he noted in the Passo Khalchi, northwest of the 
Gibelé crater. With Foerstner, Bergeat apparently considers the 
Bagno dell’ Acqua as a separate center of eruption, since it is 
indicated on the course of one of his fault-lines, though he does not 
mention it directly. 
Objections to these views.—I am quite in accord with Foerstner as 
to the general succession of the lavas, especially the earlier date of 
his ‘‘phonolites,” ‘“‘liparites,” and the ‘‘andesite”’ of Zichidi, the 
subsequent eruption of the pantellerites, and the final appearance of 
«A, Bergeat, Newes Jahrbuch, Festband, 1907, pp. 315-17. 
