Ring Around the Tub

Researchers in the Alvin submersible came across this collapsed pit of lava on the seafloor near the Galapagos Rift. Marine geologists call these shelf-like structures “bathtub rings,” because they record the different levels (or heights) of lava before it drains through tubes and fissures back into the Earth or to a downhill spot on the seafloor.(Photo by Adam Soule, Woods Hole Oceanographic Institution)