If you’re British, have good eyesight and are more than about fifty, the chances are you will remember this station ident. Back then of course, nobody knew the words “station ident” even though there were about eighteen of them, mainly for ITV companies, in this country. They’re an interesting topic in themselves, but not one I want to cover today.
What I want to illustrate probably works best with a short video clip:
As humans, we have a predeliction for discerning patterns everywhere, even where those patterns are not significant. This clip used to trigger that in me, but what I’m not clear about is whether they’re important. The black and white image emphasised the contrast for me, with black oceans clearly outlining the white continents, and it seemed to me that the Atlantic Ocean looked like a kind of triangular face looking west, which was also quite similar to how the Indian Ocean west of the Indian subcontinent looked. But of course, this could just be nothing. Maybe younger children are more likely to pick up on patterns compared to adults, but it’s still with me whenever I look at a map or globe of the world.
There are other examples. For instance, Afrika and Madagascar and the Indian subcontinent and Sri Lanka are both roughly triangular landmasses tapering towards the south with a somewhat rhomboid island to their southeast. Corsica and Sardinia are also somewhat similar islands. South America and Afrika, as well as fitting together due to having both been part of Gondwana in prehistoric times, are again both roughly triangular landmasses tapering towards the south. The same patterns repeat over and over again on the map. Another one I noticed recently which probably is spurious is the apparent similarity between the coastline of Europe and that of southwestern Great Britain. In this case, South Wales corresponds to Scandinavia, Land’s End to Iberia, the Lizard to Italy and the Isle of Wight to Crete. I’m pretty sure this one is nothing though, particularly when one considers the proportions.
All that said, one of the sources of fractal mathematics was the “Coastline Problem”. This was based on the realisation that measuring a coastline would vary according to the length of the ruler you were using. Great Britain on the crudest scale is roughly triangular, with a very approximate perimeter of 2 800 kilometres. A “ruler” able to produce a very crude but recognisable map of this island, with a length of about a hundred kilometres, yields a coastline of about 3 500 kilometres. According to the ‘CIA Factbook’, the perimeter is around 12 429 kilometres. At this point, one might find that if a ruler a mile, nautical mile or kilometre in length were to be used, different figures would be arrived at, so whereas it says 12 429 kilometres or 7 723 miles, which is correct as far as converting units is concerned, if the coastline had actually been measured twice, once in miles and the other time in kilometres, the results would not be convertible and the length in kilometres would’ve been greater. The same applies to millimetres, only much more so. One of the results of this is that it’s entirely possible to come up with similar figures for the length of the coastline from Aberystwyth to Hayling Island and Vingsand in Norway to Θεσσαλονικη by judicious choice of the right measuring sticks. Alternatively, even with the same yardstick the lengths could in theory be the same, and this is particularly plausible when comparing a fjord-rich coastline with a particularly smooth one. Also, if one considers the Mandelbrot Set, mini-versions of itself are found all over which are somewhat “morphed”, with larger regions minimised and smaller ones maximised, and this could happen to a coastline, but if that kind of thing’s allowed, it appears that anything could be made to fit.
The processes leading to the formation of the islands of Sri Lanka and Madagascar are entirely different. Madagascar is the result of rifting in the Afrikan continental plate causing it to calve off to the side like an iceberg, though one attached to the ocean bed of course. Sri Lanka has existed since Precambrian times in that position relative to the subcontinent and was joined to the land by an isthmus until recently, and is also in the centre of its plate. Nonetheless they both look superficially similar. Is it possible that there is another factor involved which leads to this kind of similarity?
As far as I can tell, although there are other continental archipelagos such as Indonesia and Japan, none are very similar to the islands I’m currently sitting in. That said, comparisons have been made between Japan and Great Britain in other ways, comparing Hokkaido and Scotland on the one hand and Wales and Shikoku on the other. Kyushu is also compared to the Six Counties on this map, but there isn’t an extra bit of Kyushu to be taken into consideration, and Scotland is no longer a different island to the one with England on it, although it was in the geologically distant past. Moreover, Sakhalin could be thought of as part of Japan geologically although there is no similar large landscape north of Great Britain which fills that rôle. That said, there are many similarities between Japan and Britain. Both have languages which are written non-phonetically under the influence of a powerful continental neighbour, both have a sense of reserve as part of their national character and both have an official state religion. To what extent, though, is this cherry-picking? This is what I’d like to get to the bottom of in all of these.
Probably the largest example of this in Earth’s geography is the fairly minor similarity between Afrika and South America. This is of course helped by the fact that they both used to be joined along an entire coastline before the breakup of Gondwana, but there are other factors. Both are roughly triangular continents straddling the Equator with a bulge in the north and a consequential human-impenetrable region in that bulge. This last point is stretching it a bit because hot deserts and tropical rain forest are opposite ends of the spectrum regarding rainfall, and the picture is complicated by the presence of rain forest in the Congo. There’s a possibly rather fruitless question regarding which bits of Afrika and South America correspond. The Amazon is in a sense the Congo of South America and there is no corresponding huge desert, although there are deserts in southern South America, none of them are that similar to the Kalahari. The Atacama is much drier and Cabo Polonio is a cold desert. The Andes are also very important for South America and there is no corresponding range in Afrika. One thing they do have in common is a thin piece of land linking them to a larger continent to the north. One might expect all of these similarities would have led to similar histories and ecologies, but it isn’t clear that this has happened. For instance, the Sahara Pump, if it happened, led to a distribution of the Afro-Asiatic language family across the Sahara and to the south about to the level of the Horn of Afrika and also into Asia in the form of Arabic, but nothing similar happened in South America. There are anteater-like animals on both continents in the form of anteaters themselves in South America and aardvarks in Afrika, and pangolins and armadillos are somewhat similar, but I don’t think there are any Afrikan “sloths”. Both of them, though, have been subjected to colonialism, although only Afrika lost people to slavery abroad due to imperial powers. Both have Hispanophone, Lusophone, Francophone and Anglophone nations, but South America is dominated by Portuguese and Spanish to a much greater extent. A lot of the differences are to do with South America being situated further to the south than Afrika, although there is of course a big overlap.
It’s conceivably instructive to look at Venus and Mars with flooded lower altitudes to see if the same kind of land forms can be identified. This is Venus:
and this is Mars:
There is a fairly clear problem with comparing either of these with Earth. In fact there are several. Both of these maps are based on the idea that 71% of the surface is covered in water as it is on Earth at the moment. However, this doesn’t mean they’re proportionately similar. That is, given that Mars is half Earth’s diameter, a proportionate amount of water would be about an eighth of ours, but that wouldn’t provide 71% cover, and on Venus, which is slightly smaller than Earth, the cover is provided by far less water because there’s less variation in altitude, possibly due to melting mountains (that’s me, not science). Taking the Martian map first, the planet is fairly neatly divided into highland and lowland regions in the south and north respectively, and again this is not a scientific judgement but I think of Mars as consisting of a single continent plus a single ocean due to its size not allowing for anything more complex. Also, the terrain illustrated depends on the absence of plate tectonics. Tharsis in the west of that map is a complex of huge volcanoes caused by a hot spot which doesn’t move and has caused a build up of a massive plateau heavy enough to have cracked the land to its east, which is the blue channel referred to as Noctis Labyrinthis followed by the great canyon, here below sea level, called Velles Marineris or Mariner Valley. Also clear is the large depression Hellas, visible on the eastern side and possibly the antipodes of Tharsis. Having a thin atmosphere, Mars shows obvious craters in the highland “continent” which wouldn’t be there if it genuinely had large bodies of water and rain eroding its surface. Therefore there isn’t really anything similar to the kind of land shapes found here.
Turning to Venus, at first glance the planet looks much more like Earth. The eastern side of the northern continent even looks rather like Siberia. However, there are many more approximately circular “islands” than there are here and the oceans are very different, being much shallower and lacking the oceanic ridges characteristic of Earth with its tectonic plates and continental drift. There are also a lot of archipelagos including relatively large islands and intermediately-sized masses of land between large islands and small continents.
Both these maps show no sign of water erosion, and there having been no continental drift the land is not like it is on this planet. Water also propels plate tectonics. It might be more informative to turn to Titan, since that alone in the solar system has both land and bodies of liquid on its surface like Earth, and it looks like this:
Like Mars, Titan’s size must be borne in mind. It’s a little smaller than Mars but its composition is very different, having substantial quantities of water ice in its make up. It’s difficult to work the consequences of this out because we’re used to water ice near its melting point, whereas Titanian water ice would be mixed with rock and therefore kind of “muddy”, and also much harder due to being well below the temperature of our South Pole in midwinter. Nonetheless, the solid surface material on Titan is eroded in a similar manner to how water erodes our rocks:
Those are pebbles, possibly of water ice (frozen water) which have been rubbed smooth by liquid ethane and methane. Titan always faces Saturn and takes just over a fortnight to orbit the planet. It’s also a lot colder than Earth and its atmosphere is thicker and therefore carries heat around the moon more effectively. Therefore, even though the surface temperature of Titan is below -180°C, it behaves as if its climate is tropical, bearing in mind also that the boiling point of methane on Titan, with its higher atmospheric pressure, is -155°C. Moreover, although we tend to think of temperature as a linear scale, it often makes more sense to see it as exponentially colder and to scale it relative to the temperatures we’re used to, because absolute zero, -273.15°C, is actually infinitely cold as it can never be reached and it always takes the same amount of energy to halve the temperature. Titan is only 5°C warmer than the melting point of methane but since its surface temperature is around a third of Earth’s, that’s equivalent to our whole planet being at 15°C. However, water is also a highly unusual substance because it expands when it freezes, which is not unique as bismuth and gallium, for example, also do it, but there are unlikely to be any celestial bodies with oceans of bismuth or gallium. Water also turns white when it freezes, which reflects heat and therefore tends to produce a feedback effect, cooling it further. Erosion and weathering from ice are therefore different from erosion would be from frozen methane. For instance, water can seep into rocks, expand on freezing and force rocks apart, and naturally glaciers can carve out U-shaped valleys and fjords. Titan would not have fjords or that kind of erosion. Nor does it have continental drift because that too requires water, meaning that there is more opportunity for erosion to smooth the surface without it being replaced by volcanism, which is also stimulated by continental drift. There are faults on Titan, but they don’t follow continental plates and there may also be volcanoes, but nothing like the “Ring Of Fire” around the Pacific Basin on Earth. Consequently something like the island of Madagascar cleaving away from Afrika won’t happen, although that doesn’t mean there wouldn’t be islands off larger landmasses on such a world.
I don’t know about you, but I find that map of Titan difficult to read. I presume that the darker patches are exposed liquid and the lighter patches land, but I’m not sure. This set of pictures, however, may make things clearer:
Despite what I said, that looks quite fjordy to me. There are also rivers running into it. This is Ligeia, a lake about a third the size of the Caspian and is the second largest body of liquid on the moon. This should be put in perspective in that in terms of proportion of coverage it’s more than four times larger and therefore bigger than the Caspian by scale. The largest body is Kraken Mare:
Kraken Mare has an approximate area of half a million square kilometres, making it almost twice the size of the Caspian in absolute terms but still only a small fraction of the size of the smallest ocean, the Arctic, even in proportion to the size of the moon. The essential difference between Titan and Earth is therefore that whereas Earth has land surrounded by continuous liquid, Titan has liquid surrounded by continuous land, meaning that comparisons of land forms are only meaningful for islands in its lakes and seas, although the shapes of the lakes and rivers are more meaningfully compared between the two worlds. The rivers of Titan seem to be much more subject to tributaries than those of Earth, which may be what gives the moon’s lakes and islands their fjordier appearance. The peninsula jutting out into the lake near the bottom left does have a larger headland to it rather than just being a finger of land, which is superficially like Iberia except that in that case the land used to be an island that collided with the rest of Europe. On the whole, it doesn’t look that familiar though. It also occurs to me that the density and viscosity of a mixture of liquid methane and ethane could be somewhat different, although the molecular weight of methane is very close to that of water. Gravity must also be a factor.
Without another Earth-like world to compare it to, it’s difficult to say what’s happening and what forms are likely or unlikely, but the considerations I’ve had to make here might narrow down the conditions somewhat. They seem to include the following:
- Relative quantity and depth of liquid.
- Coverage of surface. I’m guessing that more than fifty percent of the surface must be covered for there to be reliable continents and extensive islands.
- Plate tectonics. A lot of what’s visible on the surface of this planet is a manifestation of continental drift, which allows land to be rebuilt via volcanism and islands to surface, submerge and so forth.
- Density of liquid.
- Weight of liquid. This is not the same as density because it’s related to gravity.
- Coefficient of expansion. There may or may not be any fjords on worlds whose oceans are not made of water.
- Difference in density of liquid and solid components of the surface.
- Hardness of solid components.
- Thickness of the atmosphere – a thinner atmosphere would lead to more craters which would probably flood, although they would also be eroded quite quickly.
I haven’t been able to come to any conclusions yet about this. I can see that a supercontinent might fracture into roughly triangular continents, that island chains form from both continental drift and volcanic hot spots moving around relative to plates and various other things, but to be honest I’m no closer to being able to decide whether the apparently similar land I saw on the BBC globe in the early 1970s was mere pareidolia or a pattern which exists independently from human perception.