North Crater Flow,Craters of the Moon Lava Field. The gray, North Crater Flow lies just south of the highway in this photograph. The flow breached the wall of the North Crater cinder cone. The flow carried several large rafts of the cinder cone wall as it flowed to the east (left). The flow is a trachybasalt with approximately 65% feldspar (An30-An50), 13% olivine (Fa50-Fa55), and less than 1% pyroxene.