The central part of the blister foundered, as lava escaped through a breach to the west, leaving a remarkable depression surrounded by vertical walls of lava. Within the depression a number of lava pillars stand as rugged peaks 10-20 m high, their tops being in level with the surrounding lava surface. The sides of the cylindrical pillars are marked by slickensides formed when the consolidated surface of the lava subsided and scraped the sides of the pillars as the liquid below was drained away. Some minor craters further to the north are believed to have formed in this event. The road to the Krafla power plant lies on top of another lava from the Dal Fires.
Steam explosions cause spattering of the lava which results in the formation of scoria cones.
On the north coast of Iceland, the rift zone in North Iceland is shifted about 120 km to the west where it meets with, and joins, the mid-ocean Kolbeinsey ridge. The fault scarp exceeds 200 m at several locations, suggesting a significant dip-slip component. In fact, there are some indications that its vertical displacement may be as much as 1400 m. The total erosion of rock is estimated to have been 0.6 - 0.7 km 3 . The oldest ash layers within the canyon are about 2000 years old.