290 THE POPULAR SCIENCE MONTHLY 



THE YOLCAXIC ACTIVITY OF LASSEN PEAK, CALIFORNIA 



By Professok RULIFF S. HOLWAY 



nsrrOTWITHSTANDING vague reports of early 'settlers it now seems 

 -^^ practically certain that no white man had witnessed an eruption 

 of a volcano within the limits of California until May 30, 1914. On 

 that day Lassen Peak, a well-known old volcanic cone in the northern 

 part of the state situated about seventy-five miles southeasterly from 

 Mt. Shasta, suddenly burst into explosive action. During the six 

 months that have elapsed since the first eruption took place, including 

 one quiescent period of twenty- three days, there has been an average of 

 one eruption every three days with no indication at the time of writing 

 that the activity has ceased. The uniqueness of the phenomena as part 

 of the physiographic processes of the United States^ invites some de- 

 tailed description for several reasons. 



A natural curiosity exists concerning the events which have actually 

 occurred and also as to the most probable developments in the future. 

 Is this recent activity a sign of the rejuvenation of a long quiescent 

 volcano which is once more to pour forth its floods of lava ? Or are the 

 outbursts merely the last relatively feeble, but convulsive efforts preced- 

 ing the final extinction of the subterranean forces that formerly built up 

 the old lava cone still after centuries of erosion towering nearly two 

 miles above the level of the sea? As yet reliable forecasts of volcanic 

 activity are not made on a scientific basis, but it is hoped that the fol- 

 lowing pages will at least give a satisfactory outline of the history of 

 the region up to the present writing. 



Lassen Peak stands in the southeastern part of Shasta County, 

 nearly two hundred miles from San Francisco. According to the Lassen 

 Peak topographic sheet (a reconnaissance map surveyed in 1882-84, see 

 Fig. 1), the mountain is ten thousand four hundred and thirty-seven feet 

 in elevation and is approximately in latitude 40° 30' N. and longitude 

 121° 30' W. The immediate region is the extreme southern portion of 

 that great tertiary lava flow some two hundred and fifty thousand square 

 miles in extent, covering not only northeastern California but portions 

 of Oregon, Washington, Idaho and Nevada as well. 



1 Volcanic eruptions in Washington have been reported but apparently never 

 studied at close range. Professor George Davidson reports seeing Mt. Baker in 

 eruption in 1854 and in 1870. Pacific Coast Pilot U. S. G. S., 1899. J. C. Fre- 

 mont in his journal under date November 13, 1843, writes as follows: "At this 

 time two of the great snowy cones, Mount Regnier and St. Helens were in action. 

 On the 23 of the preceding November, St. Helens had scattered its ashes, like a 

 light fall of snow over the Dalles of the Columbia, 50 miles distant." The Ex- 

 ploring Expedition. D. Appleton tC Co., ISJ/O. 



