Colours on lava surfaces

[Bob Mehew]

I was showing some slides I have from a (tourist) visit to Þríhnúkagígur in Iceland (see Inside the Volcano) when I was asked what was the origins of the vivid colours one can see. The reds and yellows can easily be attributed to iron and sulphur. A quick on line search does suggest bacteria for thermal pools which is not relevant in this case. The one reference I did find which was sort of linked, related to cinder from ejected pyroclasts and proposed that the origin of the colours is a thin film interference effect. However, they went to say that "our findings reveal a lack of information about the chemical processes involved in the formation of the surface layer of cinders". Does anyone know of any other work on the colour of lava surfaces? I presume weathering is an important component.

 

[cap n chris]

Sadly, not, Bob, but I can attest to the remarkable colouration and iridescence which exhibits itself frequently. Some pyroducts, such as Pico Partido are fabulous. Pause the video on the TV relevant frames...