The deep Pacific 1

Basalt "bathtub rings" on collapsed lava chamber, East Pacifc Rise. Taken from submersible 'Alvin'Occasionally I’ll add comments and observations here about topical issues or things that interest me, especially those that relate to the earth sciences. In the meantime, enjoy this and the following image from a place that few people have seen up close: the floor of the Pacific Ocean. Both pictures were taken from the small (3 man) research submersible Alvin off the coast of Mexico at a depth of around two and a half kilometers. If you look carefully (click on the image to see a larger version) you’ll see what appear to be layers of rock; actually they are features geologists refer to as ‘bathtub rings.’ They form when lava pours out quickly on the sea floor and ponds in a depression, forming a mini lava lake. The surfaces of such lakes solidify quickly into basalt rock at the low temperature of the sea floor, insulating the interior, which remains molten. If the lake eventually drains in pulses, the bathtub rings – small ledges of solidified basalt lava – are left around the sides. Because it’s no longer supported, the solidified ‘roof’ collapses, as it has done here. Near the bottom of this picture you can just make out some of the broken fragments of the collapsed roof.