Idaho Bureau of Mines and Geology Bulletin Craters of the Moon National Monument, Idaho

So numerous have been the eruptions along the Great Rift that the rift might be likened to a great elongated volcano without a central orifice. It seems safe to predict that another eruption may occur in this area in the not too far distant future. The period covered by the history of our country is extremely short. Before 1914 Lassen Peak was cited in several books as an example of an extinct volcano in the United States, yet in 1914 and 1915 gigantic explosions occurred there. If these same explosions had occurred in a thickly settled part of our country they might have completely obliterated cities and killed thousands of people. Thus it is impossible to say whether a volcano is extinct or only dormant. It seems unlikely that on the Snake River Plateau, where thousands of volcanic outbursts have occurred during long ages and up to very recent time, all the volcanoes should have become extinct in the last moment of time. Instead, it appears that we happen to be living in a period of repose. The next eruption may come without any appreciable warning, although it is likely to be preceded by earthquakes. The great lava plains of Idaho, however, are very thinly settled; hence an eruption would not be likely to cause any loss of life or to destroy any great amount of property.

PLATE XX—The lava trees are tree molds that rise above the surface of the lava flow. This one, located on Trench Mortar Flat, is formed chiefly of spatter that was ejected from an adjacent fissure. Photograph by H. T. Stearns.