The Shoshone lava field is the westernmost of the young lava fields of the Snake River Plain.  It lies north of Twin Falls, Idaho and created an L-shaped lava flow 2-to-5 km in width that extends 60 km south and then west.   A single radiocarbon age of 10,130 +/- 350 years obtained for lava flows from the Shoshone field straddles the Pleistocene-Holocene boundary (Kuntz et al. 1986).  Black Butte Crater caps a lava shield that lies at the NE end of the flow field.  The vent area contains a complex lava lake that  forms a 6-part flower-petal like depression with steep-sided walls up to 30 m high that covers an area of 2 sq km.  A lava tube and channel system extends 5 km SE of Black Butte Crater and displays both roofed and collapsed portions.  The Big Wood and Little Wood rivers follow the northern and southern margins of the distal part of the lava flow, respectively.  The voluminous flow diverted the river channels so that they now join 40 km west of their former confluence.