Why do lava tubes form under some volcanic flows?
Quick Answer
The surface of a lava flow cools and hardens first, while molten lava keeps moving underneath. If the eruption continues long enough, it can drain out and leave a tunnel behind.
The Full Story
Lava tubes form when the outer skin of a lava flow solidifies, insulating the hot lava inside. As the flow continues, the interior remains molten and can travel far from the vent, sometimes for kilometres. When the eruption weakens or the lava drains away, an empty tunnel is left behind. These tubes are common in basaltic lava fields, including in Hawaii and parts of Iceland. They matter because they can transport lava efficiently and later create natural caves, skylights, and underground habitats.
Key Facts
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Suggested video title for this topic:
"Inside the volcano tunnel: how lava makes underground caves"
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