Fagradalsfjall is a tuya with NS structure due to earthquake faults having that alignment. Besides that, the volcanic systems have left NE-SW oriented slopes, as can be expected in that area. Thirdly, perpendicular lines can be detected shaping the other sides pointing NW-SE. That is a bit unexpected, except keeping the convection rolls underneath in mind. The result looks like this, when sharpened with inserted lines:
This diamond shape is quite apparent, when pointed out. The NS structure is also exaggerated with inserted lines. The red line indicates the site of eruption.
For Fagradalsfjall on wikipedia: https://en.wikipedia.org/wiki/Fagradalsfjall