NA TURE 



73 



THURSDAY, NOVEMBER 25, 1897. 



VOLCANOES OF NORTH AMERICA. 



Volcanoes of North America; a Reading Lesson for 

 Students of Geography and Geology. By Israel C. 

 Russell, Professor of Geology, University of Michigan, 

 Pp. xiv + 346. (New York : The Macmillan Co. 

 London : Macmillan and Co., Ltd., 1897.) 



PROF. RUSSELL'S beautiful volume is, in some 

 sense, a companion to Sir Archibald Geikie's 

 account of the volcanoes of Great Britain ; but whereas 

 the latter deals with volcanic relics of all ages in an area 

 the whole of which has been studied in considerable 

 detail, the former has to do only with still active vol- 

 canoes, or such as have been in activity since the beginning 

 of the Tertiary era, while in many of the districts dealt 

 with but little scientific information is available. 



The first chapter contains a most useful summary of 

 the general characteristics of volcanic action all the 

 world over, culled from the work of authorities like Judd, 

 Palmieri and Shaler, Verbeek, Button and Dana, followed 

 by an account of the shape and structure of cones, and 

 the different rock products formed by volcanic action. 

 American volcanoes do not enter much into this account, 

 but touches of local colour are not altogether absent, for 

 we learn that "while Vesuvius is regarded as a very 

 obstreperous volcanic vent, its performances are mere 

 Fourth of July fireworks in comparison with the Day of 

 Judgment proceedings of Krakatoa." 



In dealing with masses of intrusive rocks the author 

 distinguishes between dykes, sills, laccolites, plugs, and 

 siibticberant mountains, the last term applying to great 

 sculptured domes like the Black Hills of Dakota, known 

 to be based in an enormous core of granite which appears 

 to have slowly increased in bulk like "the growth of a 

 tuber in the earth" and lifted the sediments upon its 

 back. 



The next three chapters are devoted to the volcanoes 

 of North and Central America. The author does not 

 appear to have visited Central .\merica, Mexico, or 

 Alaska north of Cook's Inlet, and in his description he is 

 further hampered by the absence in many cases of recent 

 or trustworthy scientific information. Considering ihis dis- 

 advantage the account given is a very useful one, and as 

 much care lias been taken to exclude untrustworthy infor- 

 mation as to make the most of what is good. In spite of 

 Humboldt's authority. Prof. Russell thinks the story that 

 Jorullo arose in a night is not worthy of credence. 

 Izalco, in Central America, however, appears to have 

 acquired its total height of 3000 feet above the surround- 

 ing country since 1770. 



Passing on to the volcanoes of the United States, Prof. 

 Russell at once finds himself at home and amongst 

 examples which he has personally studied. His account 

 becomes more graphic and full of the results of close 

 and careful observation. Beautiful examples of denuded 

 rocks standing as columnar rock pillars are associated 

 with the lava sheets forming "mesas "or plains about 

 Mount Taylor in New Mexico. The oddly-named Ice- 



NO. 1465. VOL. 57] 



Spring Craters in Utah seem as perfect as those of 

 Auvergne, and illustrate some strange phases of eruption. 

 The lake of molten lava in one of the craters appears to 

 have slowly risen to a considerable height before break- 

 ing out an exit for itself, and relics of its former levels 

 still exist in five terraces inside the crater ring. One of 

 the lavas, too, though lying in a depressed channel, 

 evidently "spread beyond its channel like an aqueous 

 stream, and deposited, not its sediment, but its crust." 



Many interesting features of the craters near and in 

 Monro Lake, California, are described ; but we have 

 only room for one or two of the observations. Granite 

 pebbles occur in the tuffs, evidently thrown up from a 

 gravel sheet through which the volcano burst ; one of 

 the lava streams when looked at from above is seen to 

 have its scoria ridges arranged like curved terminal 

 moraines ; the lavas are mainly obsidians, and remain 

 as plugs, more or less filling some of the craters, and 

 even in certain instances rising higher than the crater 

 rim without overflowing ; where it did outflow, the lava 

 was highly viscous, and was pushed forward in thick 

 sheets, terminating in precipices between 200 and 300 

 feet high. The beautiful cone of Mount Shasta in 

 California, of which a picture is given, has not been long 

 extinct, for its most recent lavas are not glaciated. Yet 

 one of them entered the cafion of the Sacramento River, 

 reaching a distance of fifty miles, and the river has since 

 cut through this barrier and excavated a narrow gorge 

 more than a hundred feet deep in the rocks beneath. A 

 still more remarkable case of erosion is quoted from an 

 extinct volcano near Fort Union in New Mexico, where a 

 lava filled up the Mora canon to a depth of 400 feet. 

 The river has re-excavated this channel, and cut down 

 230 feet into the rock beneath. " The time required for 

 Niagara to cut its gorge . . . has been variously esti- 

 mated at from 7000 to 35,000 years." " In comparison 

 with Niagara, it is safe to say that 150,000 to 200,000 

 years have passed since the lava plunged in a fiery flood 

 into the gorge of the Canadian [River]." The descrip- 

 tions of Crater Lake, Oregon, and the extinct snow-clad 

 giants of the Cascade Range, set amongst their dense 

 forests like a "belt of emerald studded . • . with immense 

 brilliants," must be passed over, as well as the admirable 

 accounts of the vast lava fields of the Columbia and the 

 volcanoes of the Rocky Mountains, though they are full 

 of good points. 



A chapter is devoted to the noteworthy deposits of 

 volcanic ash and dust, some of which locally attain a depth 

 of fifty feet, and spread over such areas as 10,000 and 

 even 53,000 square miles. These indicate that " disasters 

 similar to those accompanying the eruptions of Conse- 

 guina and Krakatoa occurred at intervals throughout the 

 Tertiary and Recent history of fully one-half of North 

 America," leaving their traces in tracts of fertile soil and 

 deposits of considerable economic value. 



In his chapter on "Theoretical Considerations," Prof- 

 Russell adopts the idea of "potential plasticity" of the 

 earth's interior. From this he derives the pressure which 

 brings molten matter to the surface, relegating to quite a 

 secondary place the influence of steam. For many 

 reasons he considers steam an accidental and non- 

 essential constituent of lava, obtained by it when coming 



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