Is Lost City Unique?

Are there other places like the Lost City hydrothermal field? This is one of the most common questions we are asked about the Lost City. It can be answered in a variety of ways. One answer is that the geochemical processes such as serpentinization that produced Lost City are widespread on the seafloor. Many hydrothermal systems in the Atlantic Ocean and elsewhere are influenced by serpentinization and associated reactions. The Lost City is an extreme (or perhaps ‘pure’) example of something that happens all over the ocean to a lesser degree. Therefore, studying the Lost City hydrothermal field helps us to understand a globally distributed natural phenomenon.

We have not yet discovered anything else exactly like Lost City, but a few other sites have similar features. There are white carbonate deposits growing from serpentinized rocks at 5700 m deep in the Mariana Trench that resemble some of the small chimneys at Lost City. Carbonate chimneys in Prony Bay, New Caledonia host similar microbial communities as those that we have described in Lost City chimneys, but the Prony Bay chimneys are in a shallow bay and are fed by freshwater draining from shore. No two hydrothermal systems are ever exactly alike. Lost City is unique, and it is also representative of a globally important process. Just like Yellowstone National Park is unique, and it is also an instructive example for studying hot springs in general.

Lost City sits at the intersection of some major geological features that probably focus seawater into the serpentinization reaction zone underneath the chimneys. This type of system probably lasts for “only” a million years or less and then loses steam and becomes inactive. A fossilized “Ghost City” estimated to have been active in the Pleistocene Era was discovered near the Rainbow hydrothermal field, not too far from Lost City. So in one sense, we were lucky to catch Lost City while it was still very active.

Lost City and all of the sites described above were discovered more or less by accident in just the past 20 years. There has been no coordinated effort to survey the seafloor for Lost City-like systems. The ocean is just too big, and places like Lost City are too hard to find. So another equally accurate answer to the question of whether Lost City is unique is “We have no idea. We have barely even looked.” Lost City could be unique, but there could be many similar systems with their own unique properties all over the seafloor that have not been discovered. More than likely, there are places on the seafloor even more spectacular and even more scientifically interesting that are sitting down there, waiting for us to explore.

The extraordinary scientific and aesthetic qualities of Lost City have attracted the attention of UNESCO World Heritage, the International Union for Conservation of Nature, and others interested in marine conservation. The idea of seafloor conservation was mostly academic until the issue of deep-sea mining appeared (suddenly and to the surprise of many of us). The world’s thirst for battery-powered electronic devices has transformed the seafloor from an exotic, nearly fantastical world into an extractable resource. A parcel of the seafloor that includes Lost City was recently designated for mining exploration. No mining has yet occurred, but the process has begun. I am confident that nobody wants to mine the Lost City, but it’s not clear that those involved granting mining contracts are even aware that Lost City is there.

We are lucky to have discovered Lost City before we started mining the seafloor, so that it could be part of the conversation and hopefully protected. If deep-sea mining had begun earlier, or if Lost City had never been discovered, it’s hard to say what would have happened. There is no question that the deep sea contains many more amazing places that we cannot even imagine. The fundamental challenge for our future efforts to sensibly manage the seafloor is that it will remain mostly unexplored for the foreseeable future. How will we be able to protect what we haven’t discovered yet?

For more on the issue of deep-sea mining, see our page on the topic.

Here is a video of the “Imax flange”, one of the many spectacular features of the Lost City hydrothermal field. Hot water vents from the side of the massive structure named Poseidon, pools underneath this flange, and spills over the side of it.