A lava tube is a natural tunnel formed by flowing lava during a volcanic eruption. As the lava moves, the outer layer cools and solidifies, while the molten lava continues to flow beneath it. Once the eruption stops, the remaining lava drains away, leaving behind a hollow tube. These tubes can vary in size and length, with some extending for miles. They are often found in volcanic regions, such as those associated with the Hawaiian Islands or Iceland. Lava tubes can provide unique ecosystems and are sometimes explored for scientific research or recreational activities.