Pumice Can Drift Against the Waves, Lab Experiments Reveal

A lab study published in Ocean Dynamics finds that pumice from submarine volcanoes can drift not only in the direction waves travel, but sometimes backward. The work focuses on how floating pumice rafts ride wave motion, a factor that affects models used to track dispersal and potentially trace past eruptions. Researchers from the Japan Agency for Marine-Earth Science and Technology ran wave-tank experiments at the University of Tokyo’s Kashiwa campus using a wave generator at 1.0 to 1.6 hertz and pumice samples in different densities. They observed that density increases as water infiltrates pores, yet drift direction depended on wave conditions, including cases of backward movement.