Lagarfljót River is found outside the volcanic areas of Iceland. The tectonic origins can still be traced to the Snæfell area, and the river follows the same alignment formula as the Reykjans Ridge, that is the mantle rolls extending from equator.
We can then analyse the Lagarfljót River according to the relevant polygons. Polygon 1 does comprise the origins at Vatnajökull, Snæfell and the upper most reaches. Then the valleys of polygon 2. Polygon 3 makes up the central part of the river. In polygon 4 it makes a sharp turn to the north, and flows along the NS-axis to the north corner of the polygon. The tension is then over, and the river makes a wide turn to the east towards the ocean.
Red lines show up-welling, so there is clearly opposite flow compared to main drift (the east- west component of main drift vectors) of Eurasian plate found locally.