Hraunfossar – the waterfall of no river above it! The beauty and special settings of Hraunfossar can be partly explained. First we have to have in mind its position compared to the convection cell grid, as shown here on the base of a map from Náttúrufræðistofnun and Orkustofnun:
Let us zoom in on this polygon. According to the Convection Cell Model, the upwelling division line creating the Reykjanes Ridge is just at the side of the Hraunfossar waterfall. It can be seen on this Google map:
The small polygon, formed by near-crossing of four division lines between convection rolls, is subject to very clear EW-oriented tectonic settings due to the symmetry of the polygon. The river Hvítá flows accurately along the tectonic EW-axis, leading Hraunfossar to fall southwards into it. Let us now look even closer to realize what this waterfall is all about:
The lava, under which the water flows until it appears in the Hraunfossar waterfall, is considered to have flown in the 10th century. It is called Hallmundarhraun and has partly flown along a valley aligned exactly as the mantle convection line. The direction is E43.8°N. But that is not the ruling direction. A one step analysis of horizontal balance between EW-axis and the convection roll line shows the main outlines of the surrounding landscape. It is marked as a/2 and is aligned E21.9°N. The lava flow has been directed further along the E21.9°N topography alignment as it spread out along the valley of tectonic EW-axis, finally providing this excellent waterfall at the western most end of the lava.
