Page:Popular Science Monthly Volume 86.djvu/294

290

OTWITHSTANDING 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 detailed 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 preceding 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 following 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.