Interesting rock structures

Walking around on lava flows finds lots of interesting features - here are regular fractures in basaltic lava flows near Broken Top cinder cone.  These fractures are similar to those found at the Giants Causeway in Northern Ireland or Devils Tower in Wyoming, though with different shaped fractures and not as long a column as those well known structures.  It is likely caused by rapid cooling of the lava flows and these square patterns were visible over a large area.  The area is not far from some lava caves (see my next post!).  This image was taken with my 24mm lens with an exposure of 1/100 seconds at f/8, ISO 100.