 This lava field is the largest of several large beds of lava that erupted from the 53 @-@ mile ( 85 km ) south @-@ east to north @-@ west trending Great Rift volcanic zone , a line of weakness in the Earth 's crust . Together with fields from other fissures they make up the Lava Beds of Idaho , which in turn are in the much larger Snake River Plain volcanic province . The Great Rift extends across almost the entire Snake River Plain . 
