Deep Pacific Upside Down Waterfall

This passage from Helen Czerski's Blue Machine: How The Ocean Shapes Our World gives us a glimpse of the wondrous undersea universe we are just beginning to explore.

"We see upside-down waterfalls, she says. I don't understand what she means at first, and it takes me a few seconds to process the video as Deb keep talking. In those vertical chimneys, the walls crack and hydrothermal fluids come leaking out and  you get something that looks like half a toadstool growing out of a tree in an old growth forest. And suddenly I see it. This is a gigantic hydrothermal chimney looming out of the darkness, and hot water is indeed leaking out of its side. But because hot water is less dense than cold water, the hot water keeps flowing rapidly upwards. When it first hits cold water, its clearly dumped some minerals and made a ledge that sticks out- that's the toadstool shape that Deb is referring to. The water flowing upwards has had to flow outwards underneath the ledge before it can carry on upwards. But the ledge has developed a hollow on its underside like an upside-down bowl, so there is a pool of hot water there, held in the hollow as if it were filling up the inside of an umbrella. The boundary between hot and cold water shimmers like a mirror. And then the hot water is spilling out of its hollow and continuing upwards into the gloom. It really is an upside down waterfall".

Helen Czerski is watching this footage captured by a remotely operated vehicle exploring the area around the Juan de  Fuca Ridge, an undersea mountain chain a few hundred kilometers west of Seattle. Here, the Pacific and the Juan de Fuca tectonic plates diverge. Scientists are closely monitoring this ridge for seismic and volcanic activity, using a network of sensors  called the Regional Cabled Array. Deb Kelly is the Director of this project. Hydrothermal chimneys are sulfide and carbonate mineral deposits that form when hot mineral saturated sea water emerges through cracks in the ocean crust. The are common near mid oceanic ridges where the interaction of sea water and rock heated up by magma generates vigorous hydrothermal systems.

I'm only a quarter into this book and am enjoying every page of it. Highly recommended!