666 HENRY S. WASHINGTON 
covered most of the slopes of the old cone and are now seen in the 
southeast portion of the island and to the north and northwest of 
Montagna Grande. This original, large volcano was reduced to a 
large caldera with an encircling somma (about 6 kilometers in 
diameter), with gentle slopes toward the periphery but steep scarps 
on the inner side, either by an explosion or possibly by subsidence 
of the central portion, according to Stiibel’s theory. These are the 
scarps of Serra Ghirlanda, Costa Zichidi, Costa Zeneti, and Cuddia 
Nera. A similar history and a similar form at the end of the first 
stage of activity have been true of many well-known volcanoes, such 
as Santorini, Monte Vico near Viterbo, Somma-Vesuvius, Etna, Pico 
de Teyde, Taal, and many others. During this first phase and pre- 
sumably before the formation of the caldera there were formed the 
parasitic cones of green pantellerite, notably those of Cuddia At- 
talora, Cuddia Gadir, Monte Sant’ Elmo, and Cuddioli dietro Isola. 
The eruptions of the second phase began within this caldera, the 
floor of which may have been below sea-level (as in the case of 
Santorini), and which was apparently breached to the north, 
between Cuddie Nera and Gadir. These consisted largely of 
trachyte (Foerstner’s “older andesite’’), which built up the great 
mass of Montagna Grande and Monte Gibelé. I follow Bergeat in 
thinking that the latter served as the vent for most of these erup- 
tions, while Cuddia Mida may be regarded as a later parasitic cone 
near the summit of the volcano, which emitted mostly pantelleritic 
pumice. The trachytes of Monte Gibelé filled, or nearly filled, 
the large caldera, and are covered in many portions of the area with 
pumiceous lapilli derived from Cuddia Mida. 
This pumiceous outburst may be regarded as the last of this 
phase, after which the northwestern part underwent a serious 
dislocation. The block which constitutes the present Montagna 
Grande was separated from the Gibelé portion by the Passo 
Khalchi fault, and tilted about an almost east-west axis. The 
southern end was raised some 250 meters or so, forming the promi- 
nent Miliac scarp and bringing the upper edge above the level of the 
former summit of Monte Gibilé. To the north the movement was 
downward, producing the depression of the Rione di Bagno now in 
part occupied by the lake. 
