102 sD: Dana— Volcanic Action. 
Art. XI.— Volcanic Action; by JAMES D. DANA. 
THE new facts with regard to the recent eruption and subse- 
quent movements at Kilauea, make this a favorable time for a 
review of volcanic action and phenomena; and especially so 
because the Hawaian volcano and its great craters illustrate 
more fully and simply than any others that have been particu- 
larly described the ordinary principles and methods of volcanic 
activity ; and also because, although long since reported on, 
they have not yet their true place in most treatises on volea- 
noes. Vesuvius has been more accessible. The account of 
the phenomena observed by me at Kilauea in 1841, given in 
my Exploring Expedition Report,* needs no modification. But 
the conclusions after so many years of progress in science may 
well have a reconsideration. On the chief point, however— 
the essential identity in forces and laws of action between 
Kilauea and Vesuvius as well as other volcanoes-—I find no 
reason for change. In my Manual of Geology (1863) I present, 
as the causes of eruptions: 
The hydrostatic pressure of the column of lava; the pressure 
of vapors escaping in underground regions from the lavas, or 
produced by contact with them, acting either quietly or catas- 
trophically ; and the pressure of the subsiding crust of the 
earth, forcing upward the lavas in the conduit. TI also state as 
sources of movements preceding aneruption: the enlarging of 
the mass of liquid rock in its higher portions through the 
vaporizable material contained in it and imbibed on the ascent ; 
and, for aerially projectile effects, the elastic force of the vapors 
that escape by the forming and bursting of bubbles at the sur- 
face of the viscid lavas. 
In the following pages the sufficiency or not of these causes 
of activity for all voleanoes, is considered. 
* Geology of the Wilkes Exploring Expedition of 1838-1842, published in 
1849. 225 pages (4to) are devoted to the Hawaian and other volcanic islands of 
the Pacific, apart from the subject of the bordering coral reefs. ‘The time of my 
visit to Hawaii and examination of the Kilauea crater was particularly opportune 
because of the great eruption that had so recently preceded it, and which left 
behind, besides features of more ordinary character, also those rarely presented. 
I find no facts in Capt. Dutton’s report to lead me to modify my conclusions as to 
the mode of action in Kilauea, or as to the relations of the crater to those of 
other voleanoes. My tour to Kilauea commenced on the western shore at 
Kealakekua bay, and led me by the south side of the island and the southern 
slope, to Kilauea: and thence, after a study of the interior of the crater and its 
surroundings, eastward to the outflow of the great eruption of 1840 at Nanawale 
where it entered the sea. 
