354 J. D. Dana — History of the Changes in Kilauea. 



with a ladle or even a spoon.* But through one way and 

 another it usually becomes uneven in general surface, wrinkled, 

 billowy, humrnocky, knobbed, fractured, and sometimes caved 

 in or shoved out of place when fractured ; and other rough 

 features come from the adding of stream to stream. Plate IV 

 shows something of the uneven character, but not the larger 

 irregularities. Part of these rough features are owing directly 

 or indirectly to crusting by surface-cooling, thinly or deeply, 

 during the flow. Wrinkles, "billows" or domes, knobby and 

 ridg} 7 surfaces are depended on this condition, as well as the 

 tunnel-like chambers and many of the shallower fractures. The 

 fractures often lead to displacements of masses, and also to out- 

 flows of lava. In these outflows, the still liquid lava beneath 

 the crust ooz'es out and fills the crack and so makes a seam, 

 the immediate cooling at surface preventing a further flow ; or 

 the lavas pour out in larger volume and spread away in stream- 

 lets. Or the crust yields at a thin spot and the liquid stuff 

 pushes out, but becomes at once stiffened, and stopped by cool- 

 ing and so makes projecting knobs of various sizes, shapes and 

 lengths. Another source of uneven surface and cracks is the 

 moisture beneath the flowing lavas of the crater, which is 

 always present at greater or less depths since rain falls every 

 other day or oftener. 



The wrinkles and dome-shaped elevations or "billows' -1 are 

 remarked upon beyond. 



The " pahoehoe" of Kilauea is of two kinds : (1) the ordinary 

 lava of the mountain-side; and (2) that of the crater, distin- 

 guished by its separable scoriaceous glassy crust. The crust is 

 a crafc?--feature, for I have not seen it on the lavas of the 

 mountain outside. The crust, at the present time, is half an 

 inch to two inches thick, and thickest in the vicinity of 

 Halema'uma'u. As before described, it separates easily from 

 the stony lava underneath ; and this is so because the vesicles 

 along the plane of junction are much larger than elsewhere. 



The stony lava beneath the glassy crust, making the body of 

 the Kilauea streams, and many feet or yards thick is remarkably 

 solid, having relatively few vesicles. Moreover, this light gray 

 to black basalt contains commonly very little chrysolite (olivine). 

 The most chrysolitic which I observed in Kilauea rocks was 

 from one of the layers near the bottom of the precipice in 

 Waldron's ledge, 100 feet or so above the level of the Kilauea 

 floor. The stratified lavas of the walls of Kilauea, so far as 

 examined, have the same compact stony character as those of 

 the bottom, the same sparing distribution of air-vesicles. Some 

 of the. kinds, of light gray color, are almost wholly free from 

 vesicles. But while the upper part of a layer in the walls is 

 sometimes scoriaceous, it is never covered with a glassy crust. 

 * I have a spoon Med with lava that was dipped up by Mr. Coan. 



