An Geologist conducts a very-low frequency (VLF) survey of the lava...

An HVO geologist conducts a very-low frequency (VLF) survey of the lava tube to measure the rate of lava flowing through the tube. The measurement consists of two steps. First, a transect of VLF measurements across the roof of the tube is used to measure the cross-sectional area of lava flowing through the tube. Second, a radar gun is used to measure the speed that lava is flowing at that location. An open skylight is required for this speed measurement. By multiplying the cross-sectional area with the velocity, the volume rate of lava flowing through the tube can be estimated. Today's measurement showed a flow rate of 5.8 cubic meters per second (roughly 1500 gallons per second). Tracking the lava supply rate like this can be helpful for anticipating fluctuations in activity at the flow front.