The BBC News article Iceland's Okjokull glacier commemorated with plaque about a dead glacier speaks for itself.

However there is a photo in the article that caught my eye.

It shows mountains in the background and some dry flatland in the foreground. While the foreground is sunlit, some areas are shadowed by clouds, and there is what looks like it could be the apex of a rainbow along the ground with the mountains rising behind it.

Question: What might be causing this rainbow-like effect on the ground?

enter image description here

Okjokull sat atop the volcano Ok northeast of the Icelandic capital Reykjavik. Photo: JOSH OKUN

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    $\begingroup$ I'm guessing the top of the volcano has a shallow basin within it that has managed to concentrate/accumulate water vapor & serendipitously the sun was at an angle for a "rainbow" prismatic effect to occur. $\endgroup$
    – Fred
    Commented Aug 18, 2019 at 14:34
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    $\begingroup$ Low rainbow. $\endgroup$ Commented Aug 19, 2019 at 1:59
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    $\begingroup$ I think this is a trick of perspective. The glacier sat on top of the volcano, which I believe has a characteristic broad, fairly flat form. This picture is looking downslope so the refracted rays forming the rainbow are seen lower than normal. $\endgroup$
    – haresfur
    Commented Aug 19, 2019 at 2:13

1 Answer 1


This is very unusual and I've never seen it before, though I have seen other rainbow effects such as double and triple rainbows. What they all have in common is a mist of water droplets lit up by the sun. If you have ever seen a dew drop (and who hasn't) you will have noticed that when the sunlight struck it a pretty coloured light came from it. When you moved your head a little, the light changed colour. This is because white light is bent by the water droplet, and the different wavelengths bend to different degrees, so which colour you see depends on the angle of your eye to the dew drop. It's the same with a rainbow, but in this case there are millions of water droplets. It is also the case with the rainbow-like phenomenon in your photo, but instead of being high in the sky, the water droplets are hugging the ground.

So how could this happen? One possibility that occurs to me is that rain fell on hot ground, and quickly evaporated. As it evaporated into cold air, it condensed into water droplets, so you had this fine aerosol hanging low over the ground. Struck by sunlight, the white light was diffracted in the same way as in a rainbow or a dewdrop or the mist from a garden hose.


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