J. W. Shipley — Volcanic Emanations in Alaska. 141 



Aet. XI. — Some Chemical Observations on the Volcanic 

 Emanations and Incrustations in the Valley of 10,000 

 Smokes, Katmai, Alaska; by J. W. Shipley. 1 



Contribution from the Chemical Laboratory, University of Manitoba, 



Winnipeg. 



The great volcanic explosion of June, 1912, in South- 

 western Alaska which blew out the Katmai crater to a 

 depth of over 3,700 feet, distributing more than two cubic 

 miles of ash and pumice over the surrounding country, 

 left on the Behring Sea slope of the Aleutian Peninsula 

 in the Valley of 10,000 Smokes an excellent opportunity 

 for studying the chemical nature of the gaseous emana- 

 tions characteristic of the eruption. The volcanic gases 

 have been pouring out continuously from vents dis- 

 tributed over an area of fifty square miles ever since the 

 eruption and in the course of that time have built up 

 large masses of incrustants around the vents. Extremely 

 disintegrating in character, these gases have profoundly 

 altered the chemical composition of the surface rock 

 adjacent to the channels through which they find an exit. 

 Igneous rock material has been decomposed and built up 

 into altogether different chemical compounds by the ac- 

 tion of the gaseous emanations in the presence of water. 2 



The floor of the valley through which the volcanic 

 gases force their way is composed of volcanic detrital 

 matter, pumice and ash, ejected by Novarupta volcano on 

 the Behring Sea slope of the Aleutian peninsula. Nova- 

 rupta, ten miles due west of Katmai, exploded before 

 the latter and threw out much material locally. Falling 

 hot on the snow-covered northern slopes and assisted by 

 the heavy rainfall accompanying the eruption, much of 

 this ejecta slid into the valleys and formed a vast mud 

 flow. 3 The flow continued down the main valley for over 

 fifteen miles and, as it drained away, left a considerable 

 residue adhering to the valley floor. The highest level 

 attained by the flow of mud is marked on the valley walls 

 frequently 300 feet above the present level. After com- 

 ing to rest the mud was subjected to heat from below, 

 dried, and caked and over a large part of the area was 



1 The author was attached to the 1917 Katmai Expedition of the National 

 Geographic Society in the capacity of chemist. 



2 Shipley, Science, vol. 49, p. 589, June 20, 1919. 



3 Described by Griggs, Ohio Jour, of Science, vol. 19, p. 117, 1918. 



