6 CONTENTS. 
General geology — Continued. Page. 
Volcanoes among the mountains 66 
Black Butte 66 
Martin lava stream 68 
Little Canyon lava stream 69 
King Hill lava stream 70 
Blanche crater 70 
Summary 71 
Volcanoes on the Snake Eiver Plains 71 
Cinder Buttes . . 1 72 
Location 72 
Tuff cones and craters 72 
Characteristics of ejected fragments 74 
Dust and lapilli 74 
Clots 75 
Scoria 75 
Bombs ... 75 
Lava cakes 79 
Parasitic cones 80 
Lava streams 82 
( Ihemical composition 87 
Surface features 89 
Pahoehoe 91 
Corrugations and arches 92 
Aa 97 
Lava caves 98 
Depressions in the surfaces of lava sin els 101 
Margins of lava Slows terminating on a plain. . .' 102 
Margins of lava Hows terminating at the mountains 102 
Relative age of the later lava Hows 105 
Relation of the Cinder Buttes to older volcanic eruptions 107 
Market Lake craters 108 
Kuna Butte 109 
Crater rings near Cleft 110 
Older craters and lava flows 112 
Lava cones 112 
Lava sheets 112 
Lava st reams that flow r ed into water 113 
Irregularities in the thicknesses of lava sheets 117 
Changes produced in lava sheets after cooling 118 
Open fissures and faults 118 
Rock disintegration and decay 122 
Canyons and waterfalls 1 23 
Spring-formed alcoves on the sides of canyons 1 27 
Lost rivers 130 
I ' | (grading streams 133 
Soils.. 135 
Alluvial soils 135 
.Eolian soils 136 
Sand dunes ' 140 
Residual soils 141 
Summary 141 
Chemically-formed subaerial deposits 141 
Recent soil erosion 1 45 
