July 19 Érock crushing

Jenny writes:
On some evenings following ROV dives, in addition to the lost ROV dive day Saturday, we are deploying the rock crusher. We are targeting lava flows that we can identify in the AUV maps and have never been sampled, but where we are not likely to spend an ROV dive. The rock crusher is not high-tech, but it collects adequate amounts of lava for analysis and is a low-cost way to greatly expand our sample coverage. It is basically 700 pounds of lead weights and steel pipe, to which wax-tipped cores are bolted. It is deployed off the stern of the ship and lowered by winch to the sea floor, where it crushes the glassy surface of the lava flow on which it lands. Glass fragments stick to the wax, and when the sampler is recovered, we separate the glass by melting it away from the wax. 

IMG_9210_rockCrusher.JPG
The rock crusher is about to be lowered to the sea floor. It is hanging from the A-frame at the stern of the ship and kept from swinging dangerously by two tag lines. Wax-tipped cones, to which our sample will stick, bristle from the base of the pipe and encircle the clump of lead weights near the top.

IMG_9219_cones.jpg
Volcanic glass chips (black) from the lava flow surface impacted by the rock crusher are embedded in the wax (white) on the ends of the rock crusher cones (rusty). The glass chips will be scraped off and melted away from the wax in a Crock Pot. Back on shore, the chips will be cleaned, made into thin sections, and analyzed for elemental and isotopic composition.