THE " CEATERS OF THE MOON " IN IDAHO ^ 



By Haeold T. Stearns 



[With four plates] 



When in recent geological time the glaciers began to melt away 

 from the towering peaks of Idaho, floods of lava poured out of a 

 fissure on the south side of the White Knob Mountains. The cooled 

 and weathered products of these eruptions now form the unique vol- 

 canic area known as tlie " Craters of the Moon " which was proclaimed 

 a national monument by President Coolidge on May 2, 1924. It is 

 reached by a drive of 26 miles from Arco southwest along the Idaho 

 Central Highway, and is easily accessible to visitors en route for 

 Yellowstone National Park. Upon entering the monument the road 

 leaves the dusty sagebrush desert for an area of barren black cinders 

 and lava, where it winds among smooth cones and across strips of 

 rough, fresh-looking rock. The similarity of the dark craters, and 

 the cold lava nearly destitute of vegetation, to the surface of the 

 moon as seen through a telescope gives to these peculiar features their 

 name. The monument comprises 80 square miles of the most inter- 

 esting and recent part of a vast lava field which covers hundreds of 

 square miles and merges westward into the Columbia Plateau. This 

 plateau covers about 200,000 square miles and is probably the largest 

 lava plateau in the world. 



A good view is obtained from the summit of Big Cinder Butte, 

 which rises to an elevation of 6,516 feet and ranks among the largest 

 purely basaltic cinder cones of the world. To the east stretches 

 barren black lava with nothing to break its monotony except one 

 group of 3^ellow grass-covered cones which were not inundated by 

 the floods of lava, and which now stand together as a yellow island 

 in a sea of black. Farther east rises Big Butte, the sentinel of the 

 Snake Eiver Desert. A little beyond and to the northeast of it are 

 two small peaks known as the Twin Buttes. 



To the southeast extends a double line of cinder cones, many of 

 them grass covered, and all of them vents of numerous flows which 



^ A note prepared in cooperation witli the Idaho Bureau of Mines and Geology, and pub- 

 lished with permission of the Director, U. S. Geological Survey, in the Geographical Jour- 

 nal, Vol. LXXI, No. 1, January, 1928, London. Here reprinted, by permission, from that 

 Journal, with slight alterations. 



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