Using laser gun to measure velocity of lava

Using laser gun to measure velocity of lava in master tube for Mother's Day flow. Multiplying velocity times cross-sectional area yields flux of lava in tube. The cross-sectional area is interpreted from measured differences in conductivity for very low frequency radio signals passing across the tube. This skylight, called Okita Nuevo, was filled during breakout early the next day; see middle and lower below images for August 9.