I believe they are striations due to the fact that, during their formation, the cracks tend to progress in increments of centimeters at a time.
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Here's a photo I took showing the layering at Studlagil. I'm thinking that the rock faces in that 4th photo are just weathered more?
aug 31, 2025, 2:46 pm • 18 1 • view
Agree with Alex, these look like so-called « chisel marks » that are the increments of crack formation
aug 31, 2025, 8:15 pm • 5 0 • view
Lava cools, when it reaches below glass transition temperature, stress caused by thermal contraction is no longer absorbed, when too much stress has accumulated, crack propagates and stops at the limit between solid and partially molten lava. Then cooling continues, stress accumulates, next crack
aug 31, 2025, 8:24 pm • 3 0 • view