
 Parri. Sxcr.i.§2] MUD LAVAS. ~ 233 
melted lavas. On the other hand, rain or melted snow or ice, 
rushing down the cone and taking up loose volcanic dust, is con- 
verted into a kind of mud that grows more and more pasty as it 
descends. ‘The mere sudden rush of such large bodies of water down 
© the steep declivity of a volcanic cone cannot fail to effect much 
_ geological change. Deep trenches are cut out of the loose volcanic 
slopes, and sometimes large areas of woodland are swept away, the 
débris being strewn over the plains below. 
It was one of these mud-lavas which invaded Herculaneum during 
_ the great eruption of 79, and which, quickly enveloping the houses 
- and their contents, has preserved for us so many precious and perish- 
able monuments of antiquity. In the same district during the 
eruption of 1622 a torrent of this kind poured down upon the 
villages of Ottajano and Massa, overthrowing walls, filling up streets, 
and even burying houses with their inhabitants. During the great 
eruption of Cotopaxi in June 1877 enormous torrents of water 
and mud, produced by the melting of the snow and ice of the cone, 
_ poured down from the mountain. Among the débris hurried along were 
vast numbers of large blocks of ice. The villages all round the 
mountain to a distance of sometimes more than ten geographical 
miles were left deeply buried under a deposit of mud mixed with 
_ blocks of lava, ashes, pieces of wood, &c." Many of the volcanoes of 
- Central and South America discharge large quantities of mud directly 
_ from their craters. Thus in the year 1691 Imbaburu, one of the 
Andes of Quito, emitted floods of mud so largely charged with dead 
fish that pestilential fevers arose from the subsequent effluvia. 
Seven years later (1698), during an explosion of another of the same 
range of lofty mountains, Carguairazo (14,706 feet), the summit of 
the cone is said to have fallen in, while torrents of mud, containing 
immense numbers of the fish Pymelodus Cyclopwm, poured forth and 
covered the ground over a space of four square leagues. The carbon- 
aceous mud (locally called moya) emitted by the Quito volcanoes 
sometimes escapes from lateral fissures, sometimes from the craters. 
Its organic contents, and notably its siluroid fish, which are the 
same as those found living in the streams above ground, prove that 
the water is derived from the surface, and accumulates in craters or 
underground cavities until discharged by volcanic action. Similar 
_ but even more stupendous and destructive outpourings have taken 

place from the volcanoes of Java, where wide tracts of luxuriant 
vegetation have at different times been buried under masses of dark 
grey mud, sometimes 100 feet thick, with a rough hillocky surface 
_ from which the top of a submerged palm-tree occasionally protruded. 
Between the destructive effects of mere water-torrents and that 
of these mud-floods there is, of course, the notable difference that, 
_ whereas in the former case a portion of the surface is swept away, 
in the latter, while sometimes considerable demolition of the surface 
_ takes place at first, the main result is the burying of the ground 
1 Wolf, Neues Jahrb. 1878, p. 133. 
