46 NOETLING: PETROLEUM IN BURMA. 



combined with certain amount of gas pressure. In this case the mud 

 is ejected in flakes, which are thrown up high in the air and fall back 

 with a splashing noise around the vent. If the action goes on for 

 some time a cone is raised, whose surface shows the same flaky 

 structure as noticed in the fumaroles of a lava stream, and on the top 

 of which is a crater-like basin filled with mud, through which the gas 

 rises. Secondary vents frequently appear on the sides of the cone, 

 and they may in time become more important, eventually assuming 

 the position of a chief vent. This is beautifully illustrated by mud 

 volcano No. 5. It is obvious that with the rise of the cone, the 

 mouth of the vent, which ejects the mud, rises above the surface, 

 and a certain pressure is required to overcome the weight of the mud 

 in the vent. It does not seem, however, that the gas pressure is any- 

 thing very large, because a height of 40 feet from the surface to the 

 summit of the cone seems to be sufficient to counteract the explosive 

 force of the gas, which then only slowly rises in bubbles through 

 the mud. The cones generally produce streams of mud of smaller 

 or greater viscosity. When the mud in the crater has risen to the 

 rim, an overflow takes place, and the mud runs down the sides of 

 the cone, quickly at the upper part, where the sides are steep, and 

 more slowly on the base, where the gradient of the slope is very 

 small. 



The first part of a mud stream generally dries up very quickly 

 but still retaining some moisture, it forms a pavement on which the 

 subsequently ejected masses flow, without their movement beino- too 

 much slackened by the loss of moisture at their lower side. When 

 the activity of the mud volcano continues, the spasmodic gas 

 eruptions produce many spasmodic overflows of the mud in the 

 crater. The ejected mud, flowing for some time in the same direction 

 down the slope, forms, in consequence of the loss of moisture alono- 

 its sides, a narrow channel with raised sides (see plates V VI 

 and VII) inside which the later ejected mud runs down rapidly 

 till its movement is arrested along the lesser slope near the 

 ( 92 ) 



