[igitur]

The red-brown of South Africa (and I guess Argentina and Australia too) are basically midway points of their lush green regions and dry desert regions.

South Africa is as green as neighbouring Eswatini (formerly Swaziland) in the east and south coast and almost as arid as the Namib desert in the far north west.

I suppose that's stating the obvious but still interesting. And could probably add some comment about how this shows the dangers of averages of any heterogeneous data.

[mastazi]

One interesting fact is that the arid regions of Australia look much more red than most other deserts (which look more yellow, look e.g. at the Sahara or the Arabian Peninsula), this is due to the high concentration of iron oxide in the soil of many inland areas of Australia - in other words our sand basically contains a little bit of rust :-D

Edit: a more scientifically correct explanation can be found here: https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/200...

[igitur]

Does that mean if you have acid rain, it reduces back to iron?

[catlikesshrimp]

Acid rain oxydizes. Reduction is the oposite chemical reaction.

[igitur]

Ah, thanks. Then I misremembered my high school chemistry from 25y ago. I thought rust (the verb) is oxidation and that when you add an acid, it would be reduction (to get back the iron).

[barrkel]

Acid / base and oxidize / reduce are mostly orthogonal. Acid / base is about moving around protons while oxidize / reduce is about moving electrons.

There's a table here: https://www.vedantu.com/question-answer/acid-base-reactions-...

[kazinator]

"Acid" is from Latin acidus (sour, sharp, tart) by way of French.

"Oxygen" is a word invented in 1777 by Antoine Lavoisier, from the Greek oxys (sharp, acid): same thing!

Lavoisier also invented "oxide" from ox(ygène) + (ac)ide.

[LeifCarrotson]

I think the mode (after coercion from millions of colors to a smaller number of buckets) would be more meaningful than the mean.

[jcmontx]

You're right, averages in mid-sized and large countries are pretty much meaningless