August 22, 1918] 



NATURE 



497 



THE ERUPTION OF KATMAI.^ 

 ^pHE Katmai expeditions of the National Geo- 

 -*• graphic Society, under the leadership of the 

 present writer, have been exploring the district devas- 

 tated by the great eruption of Katmai in 19 12. As 

 knowledge of this eruption increases, it becomes more 

 and more apparent not only that it was one of the 

 greatest of all eruptions, but that it had many pecu- 

 liarities which set it apart in a class by itself, without 

 parallel in historic times. 



Until the eruption in 1912 there were no definite 

 records of activity in the Katmai district since, the 

 occupation of the country by white men, although the 

 natives reported that some of the volcanoes "occa- 

 sionally smoked." The district was so little known 

 that, so far as can be learned, the volcano was never 

 photographed before the eruption. Fortunately, 

 however, its altitude was precisely determined and 



previously laid undisputed claim to this distinction, in 

 every dimension. The comparative measurements 

 are : — 



Katmai 



Length 3'o miles 



Width ♦ays „ 



Circumference 8*4 ,, 



Depth 3700 ft. 



Cubage About 20 cubic miles 



Kilauea 

 2*93 miles 

 1-95 „ 

 7-85. „ 

 500 ft. 

 0'4 cubic mile 



Because of its much greater depth, the crater of 

 Katmai forms a much more awe-inspiring spectacle 

 than that of Kilauea. The two are, however, so 

 different in character that they are scarcely compar- 

 able. The bottom is occupied by a lake of hot 

 water, through • which emerges a single-breached 

 cone, the remnant of the last spasms of the great 

 eruption. 



The violence of the explosion was so great that the 

 whole of the tremendous mass thus thrown off the 



Fig. I. — Mount Katmai, the greatest of active volcanoes, after the eruption of 1512. Tlie whole of the former three-peaUed 

 top was blown away in the explosion of June, 1912, and in its place is left an enormous crater three miles long, the rim of 

 which forms the present crest of the mountain. 



its configuration was roughly indicated by con- 

 tours on the United States " Coast and Geodetic 

 Survey's- chart of the district. Before the eruption the 

 volcano was a three-peaked mountain rising nearly 

 7500 ft. above the broad valley of Katrtiai River, which 

 stretched from the sea inland to the very foot of the 

 mountains. 



In the eruption the whole summit was blown away, 

 and in its place was left an enormous crater. The 

 preliminary explorations of the National Geographic 

 Society's expedition of 1916 revealed the general condi- 

 tion of the volcano, and indicated that this crater was 

 of enormous size. In 19 17 the whole area was mapped 

 on a scale of i : 250,000, following the methods and 

 standards of the United States Geological Survey. 

 This survey showed that Katmai is the largest active 

 crater in the world, surpassing Kilauea, which had 



1 Copyright in the UniteJ States of America. 



NO. 2547, VOL. lOl] 



mountain was reduced to fine fragments. No rocks 

 or cinders of large size are to be found anywhere 

 among the ddhris. The largest piece of pumice ob- 

 served among the ejecta from Katmai is less than 

 a foot in its longest dimension. A further consequence 

 of the violence of the eruption was the very wide dis- 

 tribution of the ejecta. On the crater-rim the depth 

 of the deposit was only 45 ft., less than in many a 

 minor eruption. But Kodiak, a hundred miles to the 

 eastward, was covered by about a foot of ash, while 

 appreciable falls, accompanied by the corrosive fumes 

 of sulphuric acid, were detected so far away as Vic- 

 toria, B.C., more than 1600 miles distant. World- 

 wide atmospheric effects were also observed, but these 

 were much less pronounced than after the explosion 

 of Krakatoa. 



But in the great mantle of ash and pumice thrown 

 out over a wide expanse of country Katmai far sur- 



