108 J. D. Dana — Explosive Eruptions. 



of a volcano consists in the more or less high projection of 

 cinders or of liquid lavas, with usually a great increase in the 

 height as the crisis of an eruption approaches. In snch action, 

 there is nothing of the explosive work above described ; 

 neither is it entitled to be called a state of eruption : it is only 

 a state of activity. Stromboli is perpetually at work in the 

 ordinary way, with great variations in activity, " exhibiting the 

 nature of volcanic action in its true light ;" but it is not in 

 " perpetual eruption ;" no true eruption of this volcano, non- 

 explosive or explosive, has been recorded in recent times. A 

 volcano often gasps out its life in cinder ejections ; for this is 

 the meaning of the summit cinder cones of Kea, Hualalai, and 

 Haleakala. It is still true, however, that cases occur in which 

 it is difficult to decide whether the condition is that of ordinary 

 activity or of true eruption. 



The results of the projectile eruption of Kilauea, mentioned 

 in the earlier part of this paper (xxxiv, 359-361), need not be 

 here repeated. We learn from the deposits made by it that 

 the eruption began in bombarding style — : the projection of 

 great stones to a distance of one to two miles, ranging to a 

 height a thousand or more feet above the place 'of discharge ; 

 and ended in a widely extended shower of scoria and ashes. 

 The finer material, besides covering all the borders of Kilauea, 

 spread for miles to the southeastward, southward and south- 

 westward. It constitutes, as I learn from Mr. Baker, the sand 

 of the Kau " desert " described as ten by fifteen miles in area, 

 and makes the bed, for six or eight miles, of an excellent car- 

 riage road between the crater and the ranch nearly half-way to 

 Keauhou. 



The evidence that the great stones were from the throat of 

 the lava-conduit and not from the walls of the crater consists 

 in their comprising, both east and west of Kilauea, kinds not 

 found in the walls ; and also many blocks of lava whose vesi- 

 cles are lined with minute crystals of pyroxene and a plagio- 

 clase feldspar (as determined by Professor E. S. Dana), which 

 are proof of subjection to long-continued heat. The walls of 

 Kilauea are out of the reach of such up thrust or projectile 

 action. 



The explosive eruption of the summit-crater is of unknown 

 date. As some of the ejected stones are fifty pounds to a ton 

 in weight, it was probably similar in character to that of Ki- 

 lauea ; but the facts need further study. 



Explosive eruptions at Kilauea and Mt. Loa are exceptional 

 occurrences. In my examinations of the well-stratified walls 

 of Kilauea I found evidence only of layers of lava — that is of 

 old lava streams. But thin beds of stones and scoria might 

 occur at- intervals without making much impression on the 



