Whimsy coastlines

Scale decides on the extension of coastlines

Coastline Aztech
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Geographers like to measure: they give numbers for the economic criteria of a country, they say how high a mountain range, how deep a sea and how wide a strait is. Many of these numbers are absolute - they hardly change, or only slightly, from measurement to measurement. All the more surprising that it is almost impossible to give a statement about the true length of a coastline.

Already in 1967, the chaos theorist Benoit Mandelbrot published an article in the journal Science entitled "How long is the coast of Great Britain?" He had noticed that in various reference books quite different information was given. With the book The Fractal Geometry of Nature, he expanded the question to the description of natural forms, such as mountains, clouds and other things. The problem is not just a tricky one, it's primarily a fractal problem. Because the more you measure, the longer the coast gets. But how can that be?

Amazing thought experiment

A castaway wants to know how big his island is. For this purpose, he measures out the coast with one of the few objects washed ashore by his ship, a meter measure. He puts it neatly over and over again and counts how many times he has put it on before he has returned to his starting mark. Of course, it is difficult for him to grasp irregularities in the coast below the scale of the meter. However, if he has been able to save only a ten-centimeter-long ruler, the same action not only takes much longer, but the resulting coastline will be much higher. He can follow the actual coastline much more precisely with the shorter ruler.

The power of the surf smashes rocks and shapes the coast. © Andreas Heitkamp

So it's clear: the smaller the scale is chosen, the longer the coast line will be. This can be drifted to infinity, even down to the irregularities of the smallest grains of sand. That would not be suitable for daily life. Still, the question remains, how long the coast really is. That depends - like so much - completely on the applied scale.

Medium scale as a guide

Globally speaking, it looks like this: The individual continents have the following values ​​at a mean scale of 1: 200, 000: Display

Africa: 30, 500 kilometers

America: 104, 200 kilometers

Antarctic: 24, 300 kilometers

Asia: 70, 600 kilometers

Australia: 19, 500 kilometers

Europe: 37, 200 kilometers

Total: 286, 300 kilometers.

Looking at individual countries, it becomes more difficult. In a highly fragmented Fjord coast, the length typically varies by a factor of five, depending on whether you use cards of the scale of 1:30 million or 1: 50, 000. Wikipedia has a table with the shortest countries in the world. This table is headed by Canada with 202, 000 kilometers of coastline. These include, of course, next to the Hudson Bay and the many small islands in the Arctic Ocean. Its coastline accounts for nearly 96 percent of the country's total capita not to be confused with the political border.

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The almost 9, 000 kilometers long border with the US loses itself against it. In second place, by the way, is Norway, with at least 83, 000 kilometers of coastline beeindruck impressive for a country with a maximum extent of about 1, 400 kilometers. However, the Atlantic coast without islands and fjords would only be 2, 650 kilometers long.

Kstenland Germany

After all, with just under 2, 400 kilometers of coastline, Germany ranks 51th out of almost 200 countries. And one should not believe it, that is almost 40 percent of the total border thanks to the many islands in the North and Baltic Seas. The shortest coastline has Monaco, at about four kilometers, but at least half of its total. Incidentally, there are only 39 countries that have no coast. In addition to Switzerland and the Vatican, this also includes Mongolia, the largest country without access to the sea.

Incidentally, the data for the country's coastlines come from the CIA World Fact Book and, like so much with the CIA, the standard to which these data refer is unfortunately subject to secrecy. at least they are not specified. For the length of the common borders of countries, however, they warn that due to various measures, the border, for example, Angola-Namibia, could be longer than the Namibian border -Angola.

(Kirsten Achenbach, MARUM_Forschungszentrum Ozeanr nder, 04.04.2007 - AHE)