Here a number of geologists are making leveling measurements over an active lava shield (the profile of Pu'u 'O'o cinder cone is in the background). One geologist is using a level to sight on a barely-visible leveling rod (arrow) that is being held vertical by an assistant. Another assistant is holding another rod behind where this photo was taken, and the fourth person takes notes. The back level rod person will then leapfrog ahead and the level will also move forward to set up between them. This time-consuming process is still the best way to get an idea of the volume of a newly-erupted feature, and repeated measurements can show volume changes through time.