There are hundreds of miles in Iceland lined on each side by lava flows, ranging from soft, moss-covered lumpy fields to lunar-like expanses of rocks and sand.
This particular field is along Route 39, stretching along the road near the Raufarholshellir lave-tube cave. Most of the Reykjanes peninsula seems to be a huge lava outpouring to the sea.
The peninsula is one of the youngest parts of Iceland — the bare lava fields outnumber the soft green ones. Mossy lava fields are usually older than 2500 years (some as old as four thousand).
The lava bubbles near the road are a strange sight, indeed — cracked dome-shapes covered in moss that look as if they froze in time. Some likely house caves, others are filled in with debris and mosses. It is likely that dozens of them contain lava caves like Raufarholshellir, you just can’t get into them.