 The Craters of the Moon Lava Field spreads across 618 square miles ( 1 @,@ 601 km2 ) and is the largest mostly Holocene @-@ aged basaltic lava field in the contiguous United States . The Monument and Preserve contain more than 25 volcanic cones , including outstanding examples of spatter cones . The 60 distinct solidified lava flows that form the Craters of the Moon Lava Field range in age from 15 @,@ 000 to just 2 @,@ 000 years . The Kings Bowl and Wapi lava fields , both about 2 @,@ 200 years old , are part of the National Preserve . 
