280 jaggar: aphrolith and dermolith 



kinds, but this the writer doubts. By this is meant that the 

 gradations may be mixtures of two substances rather than stages 

 of one substance. This is only a suggestion in the present 

 condition of our knowledge, based on the discovery, reported in a 

 previous note, that the lake bottom or bench magma of Kilauea 

 was found solidified as a a, whereas the lake magma solidifies as 

 pahoehoe. 



In view of the diversity of usage cited above, and of the con- 

 fusion which results when pahoehoe crusts break up and make a 

 "fragmentary" or "block" lava not at all of aa character, or 

 when aa flows are revealed scoured bare and show "ropy" or 

 "corded" aspect without being in the least of pahoehoe origin, 

 I believe that volcanology needs a terminology scientifically 

 descriptive of the two groups of effusive magmatic bodies, and 

 capable of adaptation as adjectives, adverbs, or nouns in any 

 modern language. 



Accordingly I propose for pahoehoe the term dermolith 

 (Greek, skin + stone), to cover all those forms of effusive lava 

 which manifest subaerially a surface skin or crust, capable of 

 wrinkling or folding, as the chief distinguishing character. 



For example, dermolithic basalts are common in Hawaii, 

 Samoa, Iceland, Reunion, and on the Snake River plains, but 

 dermolithic flow has not been identified at Lassen's Peak. At 

 Mauna Loa near the vents of 1916, the lava flowed dermolithi- 

 cally in a coarse way, but exhibited a much rougher texture than 

 the characteristic dermolith of Halemaumau. On the floor of 

 Kilauea crater great fields of dermolith extend far and wide. 



I propose for aa the term aphrolith (Greek, foam + stone), 

 to distinguish those effusive lavas or crater bodies which tend on 

 solidification to subdivide surficially into complete irregular 

 lumpy vesicular units, the crust surfaces of the continuous mass 

 having protuberances of similar rugged character. 



For example, aphrolithic lava flow has been dominant on the 

 southern flank of Mauna Loa since 1868, the flow of that year 

 being partly dermolithic. It would appear also, from the ob- 

 servations of 1917, that aphrolith occupies the bottom of the 

 Kilauea lava lake and that hence the solidification of the interior 



