There is one famous waterfall still not mentioned here. It forms a semi-circle, but the sections have certain alignments. This is the main one:
Looking from above with the help of Google map, the alignment can compared with calculated direction of convection rolls underneath:
The river Skjálfandafljót makes a turn before it reaches the fault responsible for the waterfall. The alignment is the opposite of Dettifoss (but the same deviation from north), and the same as for Selfoss in Jökulsá á Fjöllum.
Again, a composition of differently oriented faults combine at the site of the waterfall.
Magic Magma 