Palaeogeography (or Paleogeography for those of you in the US)

by Jim Chapman
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During the spring of 2003, two of my children were simultaneously doing school projects about dinosaurs (and fervently wanting to be palaeontologists when they grow up!). Spurred on by this excess of youthful enthusiasm, I decided it would be fun to obtain a globe of the world, showing how it looked during the age of the dinosaurs.

The first challenge was that 'the age of the dinosaurs' is a somewhat imprecise target: it could reasonably indicate anything in the range 65 to 200 million years ago. In the end, I decided to go for 200 million years ago, because that was when the continental outlines were furthest from where they are today, and so it would produce the most bafflingly obscure map (In fact, at that time, the super-continent Pangaea was just beginning to break up - but if you knew enough to follow a link called 'Pal[a]eogeography', you probably already knew that).

The second challenge turned out to be that palaeogeographical globes are not something that anyone actually manufactures. That meant it would be a custom job. In the end, I spoke to two very helpful people at firms in the globe-making business(Eureka Cartography and Galaxy Maps). Both gave me the same message: what with all the fixed costs involved in tooling up to custom-make them, the price for one globe is the same as the price for three thousand, and that price is several tens of thousands of dollars. That was surely more than I wanted to pay. And besides, what would I do with three thousand globes of the world? It was time for plan B.

I found one site that was offering an interesting educational toy - a metal globe together with magnetic stick-on continents. But though jolly cunning, it did not meet my needs: firstly, it is quite expensive; and secondly it is - though educational - not very decorative. So plan B turned out to be to make a globe myself, and it came in three phases:

Phase 1: Obtain a map of the world as it was in the age of the dinosaurs:

Ron Blakey was most helpful here. He has produced a number of maps of the continental outlines, as they were at various times in the geological past - and best of all, his maps are available in the form of high-resolution JPEG files.

Phase 2: Transform this map into a suitable shape for gluing to a globe of the world:

I now had an image which would make a truly excellent 'cylinder of the world', but which could not be wrapped around a globe. A bit of googling made it clear that the map I had downloaded from Ron Blakey's site was a rectangular projection (also known as plate carée), and what I needed to do was to transform that into a map with a 'interrupted sinusoidal gore' projection. I even found that some kind soul (Mitchell Charity) had posted a perl add-in for The Gimp, to do that transformation. But that did not match the (Windows) environment I wanted to work in, so I wrote a program myself.

Phase 3: Glue it onto a globe of the world:

The only remaining task was to cut the map pieces out and glue them to a globe of the world. This was the result:

Modern Day:

200 Million Years Before Present:

Not exactly a thing of beauty, but an amusing way to pass the time.