Not often that one can see a river take a 90° turn, but... it is obviously possible. I think there's a waterfall in that corner.
The lava field that you can see in this shot was formed in the 10th century, after the Settlement. Its dimensions (52 km long and 7 km wide) suggest that the eruption lasted for months. A characteristic of this area are the labyrinths of caves and tunnels created by the flow of molten lava, which continued running under a crust of already solidified lava.
Exif: ISO 500 ; f/2.8 ; 1/800 ; @21mm