Science Report:
We arrived at Axial Volcano yesterday and immediately began recovering instruments on the seafloor that we had left during last year's cruise. Since we can only visit Axial with a ship once a year, we must depend on instruments to provide information on changing hydrothermal conditions between cruises. Last year we deployed nine moorings around the volcano. The moorings are lengths of special line 200 to 500 m long, anchored at the bottom with a heavy weight and held upright by several floats attached at the top and bottom. Old railroad wheels are commonly used as weights, and the floats are hollow glass balls about one-half meter in diameter. At the bottom of each mooring is an acoustic release. When it's time to recover the mooring we send a coded acoustic (sound) signal from the ship to the release, which trips a lever that disengages it from the weight and allows the entire mooring to float to the surface. We borrowed this idea from marine mammals such as whales and dolphins, which use similar acoustic signals to communicate with each other. Our acoustic signals sound like a rapid series of high-pitched "pings." We can't use radio or light to communicate because these electromagnetic signals can travel only a short way through water, while sound waves can be heard for great distances.

On the moorings we have three kinds of sensors. Temperature sensors monitor the changing temperature of the seawater. Optical sensors monitor the amount of particles in the water by shining a light into the water and measuring how much is reflected back from the tiny particles suspended in the water. These particles are created when the hot hydrothermal fluids mix with the cold seawater. Current meters measure both the speed and direction of water movements. By combining all three of these measurements we try and reconstruct the movement of hydrothermal plumes during the time the moorings were on the seafloor.

Our first day of mooring work has been highly successful. We sent acoustic signals to three releases and each mooring returned safely to the surface. It then takes some delicate ship handling to drive a 300-foot ship close enough to the floats for us to grab them with a boat hook while not running right over them! The crew on the bridge did a great job and we pulled all three moorings and their instruments back on board.

Our next task is to get the sampling gear ready for our first opportunity to sample the hydrothermal plumes since last year. We're all wondering how the hydrothermal activity has changed over a year.