362 K W. Hilgard— Geology of the Delta, 



seems likely enougli that upon the formation of a large vent else- 

 where, such a thing might happen ; especially if, as I think 

 probable, mudsprings and mud-cones form beneath, as well as 

 above the water. 



Active Cone?. — In the second stage, that characterized bv tii- 

 formation of the active eruptive cones, mudlumps offer an as- 

 pect so strikingly like that of the mud volcanoes of Tuscan \ 

 as to stagger the observer's geographical consciousness. ! 

 most striking example of the kind existed, at the time oi 

 visit, off Pass a I'Outre, on the south (right) side of the cIki 

 The island* is about an acre in extent, and besides the ; • 

 vents (of which there are seven), we perceive on the sout 

 portion the remnants of long extinct craters, in various d^ - 

 of advancement toward old age and degradation, and par 

 covered with vegetation. 



The cones on the north or channel side, at a distance, jm- 

 a glistening surface, and those possessing a central vent ■■ 

 are very regularly and smoothly conical. Of these thcr. 

 four, the diameters of the bases ranging from eighteen t^ 

 feet, and their elevation from one to two and a half feet a i- 

 the general level of the island; making the angle of tbe si<'p 

 from 5° to 8° only, instead of 25° to 35°, as given m the 

 published sketches." I have seen no undisturbed cone whose 

 slope exceeded about 12°. The slope is, of course, essentialh 

 a function of the thickness and character of the mud; which m 

 the present instance flows from the circular basin at the summit. 

 4 to 8 ins. in diameter, in a regular, creamy stream, interrupted 

 occasionally only by a gas bubble ; which, if the mud be thicK. 

 spatters it about to some extent. The mud-stream vanes trom 

 3 to 4 gallons per minute in the largest (eastern) cone, to a pint 

 or two in the less active ones ; sometimes, in running <lown tne 

 sides, it spreads over as much as I of the circumference, Dui 

 usually forms a stream 4 to 8 inches wide, serpentmg dowQ tQ^ 

 slope between banks formed by its own solidification, as doe. . 

 lava stream. As these banks grow in height by drying, on tue 

 edge of the crater, they srradually compel the mud to u- 

 higher before it can flow 'off; whereupon, after a while in^ 

 column ovei-flows at another point of the circumference, wiit 

 the same play is then repeated. In the meantime, the prevlOll^ 

 mudstream has an opportunity of consolidating, ^^^^^.^q. 

 or less, and undergoing a variety of chemical changes atpe ^ 

 dent upon the character of the water and the duration oi ^^ 

 exposure to the air, which manifest themselves m change 

 color and consistency; by these the individual strejms^ 

 distinctly defined from one another. Each one forms, ot coiu-^- 



* It was named Marindin's Lump by the crew of the U. S. Coaat Survey - 

 Varina, and I shaU aUude to it under that designation. 



