The inflation could have caused the splitting, or fissuring, to occur. Ropes on the two sides of the fissure match perfectly, indicating that no lateral movement occurred during fissuring. The next two photos show other view of this fissure. This picture shows a side view of the fissure shown in the above picture. The pahoehoe ropes on the upper surface are well displayed.
Vesicles are gas bubbles in volcanic lava or rock.
While the lava is flowing and liquid, vesicles will migrate up through the flow, leaving denser lava at the bottom and more vesicular lava at the top. At the base it is denser with few vesicles. Above it is a band of many vesicles with a large gas cavity. At the top the vesicles are smaller. A fissure divides the two halves of the formation.