During our Part 1 of the ‘Where will I be able to live’ series (which you can read here) we discussed a lot about the different climates and biomes that exist in the waters of our oceans. Today we will talk more about the geography. Specifically the geography of the Abyssal Plain, which is the vast expanse of ocean floor that lies below any continental shelf, usually at a depth of a little more than 2 miles down. But the Abyssal Plain is not a uniform flat surface. Some areas of the ocean floor have trenches or ridges. These trenches can get far deeper than the rest of the ocean, if you flipped Mount Everest upside down it would easily fit inside the Marianas Trench for example, with room to spare.

The raised areas of the ocean floor are often called seamounts.

Seamounts are underwater mountains. The tallest seamounts become islands, an example of this is Hawaii, which is a chain of islands that all started out as underwater volcanoes until they erupted and breached the surface.

When designing seasteads a lot of people tend to put all of their focus on the structure itself. Over the years that people have been talking about seasteading, many different designs have been proposed. From single hulled, monolithic structures, to single home spars, back to floating mega cities and city-ships that roam from continent to continent. But in all of these cases, a method of fixing these structures to the ground has to be created. Using steel chains to anchor ships is standard practice in today’s shipping industry. But steel chains are heavy, and locations where floating cities are likely to be built are in VERY deep water, this presents three problems. The first problem is that we have to transport the chain all the way to the drop location where we want to build our city. The weight of these chains is considerable. Imagine if we had to get 2 miles worth of steel chains and put them on a single tug boat for transportation. Depending on the size of the chains it may be impossible to fit and certainly would cost a lot of fuel to haul. Then you have a similar problem when you get it in the water. If you have 2 miles of steel chain below your seastead weighing it down, that may just be enough to completely pull it underwater, or to break an individual link in the chain which is being pulled in both directions by that amount of weight. Finally, you have not only the great expense of these chains, but you also have to deal with the fact that they will rust, meaning they will often have to be replaced at great labor and expense.

The anatomy of a common stock anchor. These anchors are designed to tip sideways when being drug so they will dig into the seabed. An anchor similar to this on might need to be used for every house sized seastead.

There are a few solutions we could come up with to address these problems. The first is to use active propulsion systems for station keeping. But this will consume a lot of fuel, likely have regulatory issues if being done in coastal waters, and involve an expensive complicated propulsion system which, if it breaks, means the structure will begin aimlessly wandering around the ocean, likely in a direction it isn’t supposed to go. For individual seastead hulls this is probably cost prohibitive, and only becomes cost effective for larger structures, but counter-intuitively, a larger structure requires a much larger spread out propulsion system, that would be providing thrust from many different areas around the city that have to be perfectly synchronized. Besides this being very complicated and putting strain on the cities joints if the propulsion is not exactly even, it would also make the survival of the city dependent upon the import of diesel fuel just to keep it stationary.

Another solution is to use different materials for the anchoring line. Half inch thick nylon rope costs about 60 cents per foot and has a break strength of about 3 and a half tons. Nylon rope is much lighter than steel and can be stored in tight coils making it more easily transportable. Using these numbers, and realizing that nylon rope can’t rust, we can start to realize how much it might cost to anchor a seastead. Let’s assume that where we are anchoring in a location 2.5 miles, or about 13,200 feet deep (4,024 meters). That puts the cost of our anchor line at $7,920. Assuming that this anchor line would last well over a decade in use, it wouldn’t be unreasonable to expect every homeowner to be able to afford this, averaging about $792 per year. This isn’t counting the cost of the anchor or labor though. There are materials other than nylon that might also fit the bill, including some specially designed neutral buoyancy anchor lines that would not put any weight on themselves due to their own length and mass, however like nylon, they have not been tested at extremely high pressures.

But there are steps that we can take to make this process even simpler. Remember those seamounts? Well some of these underwater mountains bring the ocean floor pretty close to the surface. In fact there is one in the North Atlantic that is only 29 meters deep, and another in the South Atlantic off the coast of Africa that is only 73 meters deep and in fully international waters. There are several in the southern part of the Indian Ocean that are 300-400 meters deep and still many more in the Pacific in Optimal Zones that are 200 meters deep or less. In all of these locations, we can deploy anchoring lines more easily, for less money, labor, and in safer conditions than at normal ocean depth. In addition, we would expect ocean currents to go around or slow over top of seamounts, which could also help with passive station keeping, since we may not need anchoring lines to be as strong, or anchors to be as heavy. Stationing ourselves over those areas might even open us up to using active station keeping powered by solar energy. In most if not all cases, it is easier to anchor a structure in shallow waters than it is in deep waters. Seamounts provide us a way to do this while being very far away from the coasts of established nation-states.

It is also known that seamounts play host to a more abundant marine life ecosystem than the deeper surrounding ocean waters, this can help us to build a marine ecosystem of our own and fill out ocean deserts more quickly and easily. Knowing where to find seamounts is important for these reasons, so we at Arktide have made this map of the easiest to access shallow seamounts specifically in Optimal Zones around the world. We also have a full map including deeper seamounts which is not shown here, but can be made available upon request. Just email Mitchell Suchner at mitchellsuchner@arktide.org.