 Kings Bowl Lava Field erupted during a single fissure eruption on the southern part of the Great Rift about 2 @,@ 250 years ago . This eruption probably lasted only a few hours to a few days . The field preserves explosion pits , lava lakes , squeeze @-@ ups , basalt mounds , and an ash blanket . The Wapi Lava Field probably formed from a fissure eruption at the same time as the Kings Bowl eruption . More prolonged activity over a period of months to a few years led to the formation of low shield <unk> ( ? ) in the Wapi field . The Bear Trap lava tube , between the Craters of the Moon and the Wapi lava fields , is a cave system more than 15 miles ( 24 km ) long . The lava tube is remarkable for its length and for the number of well @-@ preserved lava cave features , such as lava stalactites and curbs , the latter marking high stands of the flowing lava frozen on the lava tube walls . The lava tubes and pit craters of the monument are known for their unusual preservation of winter ice and snow into the hot summer months , due to shielding from the sun and the insulating properties of basalt . 
