Island Builders- ancient and new

(Larry G) #1

Interesting use of Baslst columns. Similar columns exist as the Giant’s Cauaseway in Scotland:


Decades ago, there was a tv show that showed that place. I don’t remember if it was NatGeo or PBS’s Nova.

I was going to mention a few more places where basalt hexagonal columns are found, but Wikipedia has a better list than i can draw from memory:

(Larry G) #3

I’ve been reading up on breakwaters and problems of reflectivity. There are several solutions similar to this example:

(Larry G) #4

Although I am not very enamoured of the idea of partially submerged sphere, toroids, ovoids etc for seasteading, I have to say I think that as a turn-key island-building solution, they may have some merit in places where the bottom is shallow enough.

I say turn-key meaning everything is built where there is access to building facilities, then it is floated to the location completely built. I imagine it being constructed so as to draft no more than 10’.

I think the Marinea Bahamas project area would be a good candidate for it. I can envision a toroid with rounded bottom being floated out into location, and set down in a controlled (reversible) scuttle. Housing can be built into the donut part of the toroid, with a beach built into the outer part of the ring (even if the beach is just concrete rather than accumulating sand.

The inner area would be a shallow, more or less conical area terraced into park/cropland, working space, and a freshwater reservoir in the middle. The freshwater reservoir could be supplemented with “underground” reservoir in the bottom of the toroid’s outer ring which would be the ballast tanks for placing (and moving if necessary).

This freshwater ballast could always be pumped out to floating polymer bags without much loss if you needed to re-float and move the structure. These bags can be towed for some distance as freshwater floats on seawater. Even though the freshwater is slightly lighter than seawater, the additional mass of the toroid/tank walls would still make it heavier than seawater when filled.

Shape: The bottom could be smoothly rounded for leveling purposes, or could have a skirt built into it like many oil rig platforms do. This is a shallow water solution either way. It could have a smoothly rounded or ovoid outer perimeter, or it could include some extruded breakwater/bay areas, but these add points of engineering complexity and potential points of failure.

In the Bahamas reef area already under consideration, there are areas where the water is only 10-30’ deep. That’s not too bad for even a home scale build. A torus 50 feet in diameter (1962 ft^2) is the area of an average US home, almost 1/4 the size of an average suburban lot. Given an aspect ratio of 1/3 that would make it 16 ft high, or go with a 1/2 aspect ratio for 25 ft high. Sunk to 15’ depth, that leaves 10’ above the water, which is low but almost the average in the Bahamas. You can play with the aspect ratio per your own specific location and requirements. You shouldn’t be able to get waves more than 7’ high above average high tide in an area that is only 15’ deep.

1962 ft^2 overall footprint with 1/2 aspect ratio: 25’ high gives you two usable floors and sub-floor ballast tanks of 5’-7’ in the bottom. Housing being up high in a ring around the outside still allows a good 10’ of enclosed space all the way around the ring. About 648ft^2 in this top level (assuming 35’ outer diameter, 20’ inner diameter). Almost 3 times this much on the lower floor (pretty much the entire footprint at 1962 ft^2). So one room wide, along the length of the rim, and a 5’ wide terrace (about 236 ft^2) on ground level for this floor on the inside of the ring. Conical pond that is about 10’ in diameter by 10’ , filled up to a couple feet below the inner terrace, holds nearly a thousand gallons. More if you make the sides steeper rather than conical. The pond can easily have a platform constructed over it for further workspace or greenery. Shading the pond keeps the water temps a little cooler and slows algal growth. The roof of the top row is yet more space for activities and items that don’t need to be sheltered from wind.

Edit to add: Scratch the conical pond, just make it a cylinder. More than 12 tons in easily pump-able/removable ballast and 3 times as much freshwater storage as a cone. Easier to engineer and more stability, too. I was typing this up from a vague idea before I had enough coffee this morning. Also corrected some math for scaling.

The top floor could be designed mostly for group spaces, work spaces that have direct access to air and light on the inner and outer face, and the next floor down is wider and contains sleeping quarters.

You can always add breakwaters, play with the outer slope angles for more or less “beach-like” qualities. Building the housing into the outer, upper ring of the torus means you have a nice view/vantage for homes that feel open and inviting, while you put more of the systems, reservoirs, and machinery that maintain the place lower in the structure for both buoyancy/stability characteristics and because those are places to do work and the place to relax is up in the air and sun. The terraced inner slope (mimicking a volcanic island’s caldera & lake) is also light and airy, but sheltered enough from winds to allow lots of activity and growing things. If the inner bit is open to the air, you can do freshwater aquaponics and aquaculture, and use to irrigate crops on higher terraces which trickle back down into your lake/pond, while freshwater reservoirs inside the shell are purified and sanitized to drinking water standards. You don’t want to waste energy on doing that for irrigation water, but the larger volume of freshwater is an overall safety margin.

This structure would serve as a residential center point for further structures- breakwaters, floating real estate anchored or attached, floating docks for mooring alongside, etc. These things could pop up like mushroom in a fairy ring and BE the breakwater for other floating structures. The construction cost should be within sight of building a home on land, or a live-aboard vessel.


Interestingly, these are giant crystals of the mineral Basalt – the same stuff some folks are considering/trying as non-rusting ('cause no metal) reinforcing bars.

That said, I hope the Basalt fiber people aren’t melting down such giant crystals. (I think those are very cool, though I barely recall seeing such in California, as a child.)

(Larry G) #6

Scale up the idea above to 100’ diameter torus.

Now it’s 7850 ft^2 footprint. The size of the average US suburban lot. Still built on a scale of floating construction that is seen regularly (100’ LOA) and much less material than the average small office building. It gives you the option to change the height/width aspect ratio while still maintaining enough depth for the target location. More horizontal space is generally better than more vertical space. It’s taller but still drafts less getting to the location, which means more options on where to place it and how deep.

Note on the rounded bottom rather than purely flat- this gives us an inverted arch that holds up the structure in compression, which is where concrete is strongest and best-suited. It should make the best of a bottom that isn’t perfectly engineered to accept and support it without creating pressure points where the stress on the bottom exceeds the strength of the hull. The bottom still needs some discretionary survey and preparation. The arc of the bottom of the hull does not have to match its radius as if it were meant to be a perfect sphere, a flattened torus is going to provide the best materials cost/benefit ratio.

I don’t know what the upper limit on scaling this idea may be. Just an impression would say it could probably be done almost up to the size of a sports arena without any real break-throughs in construction technique.

I started the first post on this idea with 100’ diameter in mind, conflated some of my numbers between 50 and 100 ft diameters, had to go back a bit and re-do them. So if there’s any mistake in math, that’s probably why and feel free to point it out. I had to diagram it on graph paper for some conceptualization, I don’t have an electronic version of the diagram yet. It’s a lot more attractive at the 100’ diameter.

If you can get to 235’ in diameter, you have an entire acre, can get the torus even flatter, still within the lengths that commercial shipping is ordinarily and customarily built (although much more massive than average due to being a circular structure rather than a boat shape).

(Matias Volco) #7

When I read “Island Builders” I thought it meant floating island and was sure I’d see something about the Uros Islands (Uru) of Lake Titicaca (or perhaps another mention of Richie Sowa)

I find it interesting to see how they use the same material in slightly different ways to make almost everything.
I find it inspiring, but the houses on a platform are only apt for the pond conditions of the very tranquil and wave-free, possibly wind-free Lake Titicaca.

What shape and material would the Uru use facing the conditions oif the high seas instead of a valley lake?


You see all that was left of Sand Island was the riprap rock rubble around the base of the lighthouse, put there as the island was disappearing. None of the material around the base of the lighthouse is the original Sand Island:

And this is near to being finished:

So i see no reason Minerva Reef should have failed, except they did not have a navy to repel an attack. Pics are from here. Google maps is here.

(Jonas Smith) #9

One person with a hunting rifle could have repelled the attack…Michael Oliver was either an idiot or a con artist.

(Larry G) #10

Something to keep in mind; good soil has certain required elements, and it can be created or improved from almost anything that will physically hold moisture while you build the organic content.

If one were to artificially enclose an atoll previously open to the ocean, you would essentially have a polder:

If you enclose it and fill it in, you would want some way to balance hydrostatic forces with the sea outside the ring to prevent saline encroachment. Massive desalination efforts might be one way to increase the freshwater content of the soil to balance the tendency of saltwater to filter in.


Or the use of flower pots. :smile:

Basically, let the natural rain maintain the natural ground water, and for your use, you supply your own water. Sure, it’s entirely possible for the first 50 years, you let your used potable fresh water percolate in too.


Yanno, doing a peacefull secession from an existing island nation to being a new island nation would give you the right to be your own registrar. However minimal your laws are, they’d be a recognised legal standard among all the floating cities that pay you a tribute to fly your flag.

(Matias Volco) #13

better to enclose it all in a big flower pot

(Larry G) #14

That would be the idea of enclosing an already mostly-closed atoll.


An inch of water over an acre of farm is 3600 cu ft, or 27,000 gallons.

Do you really want to put a tax on the citizens so you can make 27,000 gallons of desalinated water, and then pour it out on the ground, so it can benefit the ground 20ft or 30ft down, that they will never see?

Or might it be better to put it into a 16ft^3 tank, or a swimming pool, or freshwater fish farm, or distributed flowerpot-hydroponics?

I’ve lived places where the tarmac drains fed watermakers, where the swimming pool was backup desal water, and the fire mains were salt water. Elwar prolly has too. I suggest you put the water table off the priority list entirely, and when you get a golf course, it’s irrigation water will feed the water table.

I mentioned an inch because it’s a good thunderstorm, or a week of drizzle. An acre is 208x208 ft, or an average tiny island that won’t sustain much life.

(Matias Volco) #16

I’m not suggesting a polder. That only solves the problem laterally

(Larry G) #17

I wouldn’t suggest making it a priority over other things. But water gets used, and if you have a solid desalination plan, it would be better to pour that used freshwater out and make more than try to recycle/reclaim it again. You want to make sure saltwater is being pushed out or you won’t have much long term success in growing things.


Well, part of my point in mentioning hydroponics and flower pots was initially to not grow things on the ground. If you are building the island yourself, it’s been washed over with salt water far more than it’s been rained on, and same if you are buying a drowning island to build up like Sand Island was done. There’s a 100% chance that nothing will grow anyhow.


Sand Island didn’t last. By Sept the next year, all that sand added was gone. See here.

(Larry G) #20

Thus the reason I have been researching haliculture and halophytic agriculture. There are quite a few plant species you can use to stabilize a shoreline if you’re not worried about displacing existing ecological balance.