November i6, 191 i] 



NATURE 



79 



RECENT THEORIES OF VOLCANIC ACTION.' 



F'^IFTY years ago it appeared as though the volcanic 

 problem had been completelj' and satisfactorily 

 solved. Granted a cooling globe in which a solid 

 crust covered heated matter, actually or potentially 

 liquid, then the influx of sea-water through fissures 

 in the crust seemed to account for all the phenomena 

 observed during a volcanic outburst. Observations 

 had then been almost wholly confined to the small 

 group of Mediterranean volcanoes; but as our know- 

 ledge of volcanic action and terrestrial physics has 

 grown with more continuous study over wider areas, 

 these conclusions, as well as the premises on which 

 they were based, have long since failed to satisfy 

 students of geophysics. 



One of the chief factors in bringing about this 

 revolution in opinion has undoubtedly been the 



and other observers. In the study of the highly heated 

 lavas of these volcanoes, an explanation has been 

 found of the " slaggy " and "ropy" varieties of lava, 

 as well as of the peculiar types known as "pillow- 

 lavas " formed when they flow into the sea (see 

 Fi.er- 3)- 



In addition to the new light thrown on volcanic 

 action by the observations carried out in recent years 

 on these Pacific volcanoes, there have been, during 

 the last thirty years, three great outbursts of igneous 

 activity, attended by phenomena of startling and un- 

 expected character, which have served to awaken 

 geophysicists to the fact that the old and simple 

 theories formerly accepted stand in need of revision or 

 replacement. 



In 1883 the tremendous outburst of Krakatoa, in 

 one of the great highways of the world's commerce, 

 supplied opportunities for the study of the explosive 



i P^toio.] [E. Moses, Hilo. 



^ Fiv-,. I. — Panoramic photograph of Halemaumau (the open lake of lava in the crater of Kilauea) on January 13, igio, with Mauna Loa in the background. 

 The nearly circular lake was about 200 metres in diameter ; its surface was estimated to be about 25 metres below the rim of the crater. 



Photo. \ [E. Moses, Hilo. 



Fig. 2. — Panoramic photograph of Halemaumau on February 20, 1910. The lake level fallen about 30 metres below the surface of the ''black ledge " 



ot Kilauea in the foreground. 



ystematic study of the remarkable volcanoes of the 

 lawaiian islands, for which we are especially in- 

 ebtcd to the geologists of the United States. In 

 be great "pit-crater," or "sink," of Kilauea, always 

 pen to inspection, we find the explosive action and 

 scape of gases reduced to a minimum, such "sinks" 

 resenting the most marked contrast to the explosion- 

 prmed craters of Vesuvius and .Stromboli (see Figs, i 

 nd 2). Equally striking is the difference between the 

 reat flat Hawaiian domes, rising above the ocean- 

 oor to the height of the Himalayas, with slopes of 

 am 1° to 4°, and the steep conical piles of Chimbor- 

 and Cotopaxi. .Vnother volcano of the same type 

 tile Hawaiian, Matavanu, in the Samoan group, 

 :is been recently described by Dr. Tempest Anderson 



The Nature of Volcanic Action." By Reginald A. Daly. Proceedings 

 le American Academy of Arts and Sciences, vol. xlvii., No. 3, pp. 47-123, 

 me, igii. (Boston, Mass.) 



NO. 2194, VOL. 88] 



type of volcanic action, which is so strikingly different 

 from the effusive type of Hawaii and Samoa. With- 

 out any outflow of lava, fused matter was shot to the 

 height of from sixteen to twenty-five miles into the 

 atmosphere, the shocks producing air-waves that 

 travelled two or three times round the globe. In this 

 great uprush of gases, the molten materials were 

 reduced to such a state of fine division that they were 

 diffused through the whole of the atmosphere of the 

 globe, giving rise to those wonderful sunset glows 

 that will be so long remembered. In this great out- 

 burst, the hydrosphere was affected to a much less 

 extent, and the lithosphere scarcely at all — for earth- 

 quake shocks, as distinct from air-concussions, were 

 almost, if not entirely unfelt. 



Five years later, in 1888, occurred the singular 

 eruption of Bandaisan in northern Japan. In this 

 case the sudden outburst of gases did not carry with 



