A view over the main rift of Thingvellir, extending to the lake Thingvallavatn.
The location of Thingvellir is quite special and makes us combine geology and history in a very special way. But why are the walls of the rift so prominent in the area of Almannagjá and its surroundings? It can be seen on geology maps, and by analyzing the convection cells underneath. Whereas the lake is at the western edge of the Western Volcanic Zone of Iceland (with direction α), the volcanic system of Hengill (with the direction (3/4)α, a large scale rift valley (with the direction (1/2)α, and the NS axis of the relevant polygon of mantle convection cell division lines.
Thingvellir can therefore be explained by referring to the basic formula of convection cells and the derived main tectonic alignments:
Can you find Thingvellir there? And the relevant tectonic alignments?
Please check a detailed geologic map of Iceland and trace the relevant tectonic settings. Then you see why Almannagjá and Hrafnagjá are located where they are 🙂