MUD VOLCANOES.— VOLCANOES. 



at the distance of six [German] miles. Great 

 blocks of stone, torn from their foundations be- 

 neath, were scattered widely around. Similar 

 blocks are observed about the now slumbering 

 mud volcanoes of Monte Zibio, near Sassuolo, 

 in the north of Italy. The second state, or 

 that of activity, has continued for 1500 years 

 in the mud volcano of Girgenti (Macalubi), in 

 Sicily, which is described by the ancients. 

 Many conical hillocks of 8, 10, and even 30 

 feet high, though the height as well as the form 

 of these varies at different times, are there seen 

 arranged near one another. From the superior 

 very small basin, which is full of water, along 

 with periodic escapes of gas, there are periodic 

 streams of clayey mud discharged. The mud 

 of these volcanoes is generally cold, but oc- 

 casionally, as at Damak, in the province of 

 Samarang, island of Java, it is of high tem- 

 perature. The gases, which escape with a 

 rushing noise, are also of different kinds — hy- 

 drogen gas, mixed with naphtha, carbonic acid, 

 and, as Parrot and I ascertained (in the penin- 

 sula of Taman and the South American Vol- 

 cancitos de Turbaco), almost pure nitrogen 

 gasC*"). 



Mud volcanoes, after the first forcible out- 

 burst of flame, which perhaps is not common to 

 all in the same measure, present the observer 

 with a picture of an activity of the interior of 

 the earth that proceeds incessantly but feebly. 

 The communication with the deep strata in 

 which a high temperature prevails is speedily 

 interrupted again ; and the cold discharges of 

 mud volcanoes seem to indicate that the seat 

 of the phenomenon, in its state of continuance, 

 cannot be very remote from the surface. The 

 reaction of the interior of the earth upon its 

 outer crust is exhibited in a very different de- 

 gree of force in the proper volcanoes, or burn- 

 ing mountains ; in other words, in those points 

 of the earth where a permanent communica- 

 tion, or, at all events, a communication that is 

 renewed from time to time, is established be- 

 tween the surface and the deep focus of igni- 

 tion. We must carefully distinguish between 

 more or less exaggerated volcanic phenomena, 

 such as these : Earthquakes, hot springs and 

 jets of steam, mud volcanoes, the appearance 

 of unopened dome-shaped trachytic mountains, 

 the opening of these mountains, or the upheaval 

 of basaltic beds as craters of elevation, the 

 final rise of a permanent volcano within the 

 upheavement crater itself, or amongst the frag- 

 ments of its previous constitution. At differ- 

 ent times, along with different degrees of ac- 

 tivity and force, permanent volcanoes throw 

 out jets of aqueous vapour, acids, glowing 

 ashes and scoriae, and, when the resistance can 

 be overcome, fiery streams of melted earthy 

 matters. 



As a consequence of a great but local mani- 

 festation of force in the interior of our planet, 

 elastic vapours raise either single parts of the 

 crust of the earth into dome-shaped, unopened 

 masses of felspathic trachyte and dolerite (Puy 

 de Dome and Chimborazo) ; or the upheaved 

 strata are broken through, and inclined out- 

 wards in such wise that upon the opposite inner 

 aspect a steep rocky edge is produced. This 

 edge then becomes the boundary of an upheave- 

 ment crater. When this has risen from the 



bottom of the sea, which does not by any means 

 happen in every case, it then presents the 

 whole of the characteristic physiognomy of the 

 upheaved island. This is the origin of the cir- 

 cular form of Palma, which Leopold von Buch 

 has described so carefully and so ably, as well 

 as of Nisyros, in the jEgean Sea("^). Occa- 

 sionally, one half the ring-like edge is destroy- 

 ed, and in the bay which the sea that has flow- 

 ed in then forms, the social coral insects es- 

 tablish themselves, and produce their cellular 

 dwellings. Craters of elevation on continents 

 are also frequently found filled with water, 

 when they contribute to beautify the landscape 

 in an extraordinary and quite peculiar manner. 

 Their origin is not connected with any spe- 

 cial mountain formations ; they break out in 

 basalt, trachyte, and leucitic porphyry (Somma), 

 or in doleritic mixtures of augite and labrador. 

 Hence the very dissimilar natures and external 

 forms of this kind of crater edge. " No erup- 

 tive phenomena take place from such bounda- 

 ries ; through them there is no permanent chan- 

 nel of communication established with the in- 

 terior, and it is only very rarely that traces of 

 still active volcanic power are discovered in 

 the precincts or within the circuit of such cra- 

 ters. The force competent to bring about such 

 important effects must long have gathered it- 

 self together, and gained strength in the inte- 

 rior, before it could overcome the resistance of 

 the superincumbent masses. On the formation 

 of new islands, it throws up granular rocky 

 masses, and conglomerates (layers of tufa full 

 of marine plants) above the level of the sea. 

 Compressed gases escape through the crater 

 of elevation ; but a mass of such magnitude 

 thus upheaved sinks down again, and closes 

 forthwith the openings which are only formed 

 for such manifestations of force. No volcano 

 is produced"(i»2). 



A proper volcano only arises where a per- 

 manent connection is established between the 

 interior of the earth and the atmosphere. Here 

 the reaction of tlffe interior upon the exterior 

 proceeds for lengthened periods. It may, as 

 in the case of Vesuvius (Fisove)'^^, be inter- 

 rupted for centuries, and exhibit itself anew 

 with renovated vigour. In the time of Nero it 

 was already customary, in Rome, to rank .^tna 

 among the number of the gradually-expiring 

 volcanic mountains(^^*) ; JGlian, indeed, at a 

 later period, maintained that the seamen began 

 to see the sinking summit at a less distance on 

 the high seas than formerly(^^*). Where the 

 evidence of the eruption, I might say the old 

 scaffolding, has been perfectly preserved, the 

 volcano shows itself rising from a crater of el- 

 evation ; there a high rocky wall, a rampart of 

 greatly-inclined strata, surrounds the isolated 

 cone in the manner of a circus. Sometimes 

 there is not a trace of this circus-like inclosure 

 visible, and the volcano, not always conical in 

 figure, then arises as an elongated ridge imme- 

 diately from the elevated platform. This is 

 the case with Pichincha, at the foot of which 

 stands the city of Quito. 



As the nature of mountain masses, in other 

 words, the combination or grouping of simple 

 minerals into granite, gneiss, and mica-slate, 

 into trachyte, basalt, and dolerite, independent- 

 ly of present climates, and under the most dis- 



