In 2010 Eyjafjallajökull eurupted. Its location is interesting, as the crater is in the middle of a polygon. It is directly south of Hekla, which is in the north corner of the same polygon. The craters of Vatnafjöll and Tindfjöll are also on that line.
The elliptical form around the crater of Eyjafjallajökull, exactly in the middle of the polygon. Hekla marks the northern corner of the polygon.
Countless examples like this one show how the convection rolls shape the surface.
I have a BS degree in geology and provide this website about my analysis of convection rolls in the Earth's mantle and how they affect the surface.
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