The Colors of Alluvial Fans

Alluvial Fan, Iceland

Yesterday I posted an image of an alluvial fan in Iceland and  today I am posting another which looks entirely different. These landforms are shaped by the deposition of sediment carried by rivers as they flow from higher areas to lower elevations. In Iceland, these alluvial fans  occur at the mouths of glacial rivers, where the rivers deposit the sediment eroded from the surrounding mountains and glaciers. It is fascinating that the meltwater can be stored to create subglacial, englacial, and proglacial lakes, or they can be suddenly released as catastrophic floods and proglacial fluvial systems.

Some of these flows contain  basaltic minerals,  clays, calcite and other  crystalline phases  like basaltic glass, palagonite, nanophase iron which can cause almost psychedelic colors. The colors come from different mineral deposits. Red and brown colors: Iron and sulphur  which assimilate with the oxygen of the atmosphere. The sulphur creates yellow colors and the iron red and brown hematite. Grey colors are created when sulphuric acids dissolve the basaltic rock. Light colors and  mainly created by Silica and  Calcium, and sometimes also Gypsum. Shades of blue can be from Cadmium.
There are lots and lots of these outflows all throughout Iceland along the coast because of the Vatnajokull Glacier which is the largest icecap in Europe.

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