ILLUSTRATIONS 
Page. 
Plate I. Sketch map of southern Idaho, showing approximate extent of 
Snake River lava 13 
II. A, Snake River Canyon below mouth of Rattlesnake Creek, look- 
ing west; B, Snake River Canyon near Hagerman, Idaho, looking 
northwest 24 
III. The Thousand Springs, Snake River Canyon, Idaho 26 
IV. Shoshone Falls, Snake River, Idaho 28 
V. A, East Butte, Idaho — an old rhyolitic volcano surrounded by basalt; 
B, Big Butte, Idaho —an old rhyolitic volcano surrounded by 
basalt 34 
VI. North wall of Snake River Canyon, Ada County, Idaho 52 
VII. South wall of Snake River Canyon, Halls Ferry, Idaho 54 
VIII. A, Remnant of Snake River lava, King Hill Creek; B, Block of 
columnar lava, Snake River Canyon 60 
IX. A, Wall of Canyon Creek Canyon near Mountain Home, Idaho; 
B, North w r all of Snake River Canyon near mouth of Little Can- 
yon, Idaho 64 
X. Cinder Buttes, Idaho, looking southeast 72 
XI. Sections of volcanic bomb, Cinder Buttes, Idaho 76 
XII. Volcanic bombs, Cinder Buttes, Idaho 78 
XIII. Blistered lava surface and corrugations on lava stream, (Under 
Buttes, Idaho 90 
XIV. A, Lava expanded by steam on entering water; B, Pressure folds, 
surface of recent lava flow, Cinder Buttes, Idaho 92 
XV. A, Pressure ridge in Snake River lava near Market Lake Craters, 
Idaho; J5, Pressure ridges in Snake River lava near Big Butte, 
Idaho 94 
XVI. A, Market Lake Crater, Idaho; B, Stratified lapilli, Market Lake 
Crater, Idaho 108 
XVII. A, Kuna Butte, near Cleft, Idaho; B, Crater rings near Cleft, Idaho, 
Kuna Butte in the distance 110 
XVIII. Lava cone, Snake River Plains, near Arco, Idaho 112 
XIX. A, Pillow-like folds in lava stream that entered water; B, Section of 
spindle-like roll of lava from a lava stream that entered water ... 114 
XX. Section of a lava stream that entered water, Bliss, Idaho 116 
XXI. Lava resting on undisturbed lake beds, Canyon Creek, Idaho 118 
XXII. Twin Falls, Snake River, Idaho 124 
XXIII. A, Fault scarp of basalt near Cleft, Idaho; B, Little Canyon, looking 
south into Snake River Canyon, Idaho 126 
XXIV. Blue Lake alcove, looking south into Snake River Canyon, Idaho. . 128 
XXV. A, Recent stream erosion near Howell, Idaho; B, Waterworn masses 
of basalt in Snake River Canyon near Hagerman, Idaho 146 
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