Lava tube facts for kids

A lava tube is like a natural tunnel or cave made by flowing lava from a volcano. Imagine a river of hot, melted rock moving underground! When the lava inside these tunnels drains away, it leaves behind an empty cave. These amazing tunnels are also sometimes called pyroducts.

How Lava Tubes Form

Lava tubes are a special kind of lava cave. They form when very runny lava flows from a volcano. There are two main ways this happens:

• Crusting over of lava channels: When lava first erupts, it often flows in open channels, like rivers. The edges and top of these channels start to cool down and harden, forming a strong crust. This crust acts like a roof, creating an insulated tunnel. The hot lava keeps flowing underneath, staying melted because the crust keeps the heat in. These types of tubes are usually found closer to where the lava first came out of the volcano.

• Underground pāhoehoe flows: Sometimes, lava flows in wide, flat sheets called pāhoehoe flows. This type of lava has a smooth or ropy surface. As the top layer cools and hardens, the lava underneath keeps flowing. If the lava flow gets blocked, the hot lava can break out at a new spot. The lava then flows from the old source to this new breakout point, creating an underground channel. This channel eventually becomes a lava tube.

What's Inside a Lava Tube?

A large area of lava flows often has a main lava tube with many smaller tubes branching off it. These smaller tubes carry lava to different parts of the flow. When a volcano stops erupting, or the lava changes direction, the lava inside the tubes drains away. This leaves behind empty caves.

Inside these drained tubes, you can often see cool features:

• Flow lines: These are like step marks on the walls of the tube. They show the different levels where the lava flowed before it drained away.
• Pāhoehoe floors: The bottom of lava tubes is usually smooth or ropy, just like the pāhoehoe lava that formed them. Sometimes, rocks from the ceiling might have fallen and covered the floor.
• Lavacicles: These are like stalactites made of lava! They hang down from the ceiling of the tube. They can look like splashes, shark teeth, or even thin tubes. Lavacicles are the most common type of rock formation you'll find in lava tubes.
• Stalagmites: Sometimes, drip stalagmites can form on the floor, usually under tubular lavacicles.
• Mineral deposits: You might also find shiny crystals or crusts of minerals on the walls or as small stalactites and stalagmites.

Lava tubes can be quite big! They can be up to 14–15 metres (46–49 ft) (about 45-50 feet) wide, though they are often narrower. They can also be found anywhere from 1–15 metres (3 ft 3 in – 49 ft 3 in) (about 3-50 feet) below the ground. Some lava tubes are incredibly long. For example, a tube from the Mauna Loa volcano in Hawaii goes for about 50 kilometers (31 mi) (about 31 miles) to the ocean! The Cueva del Viento–Sobrado system in Tenerife, Spain, is over 18 kilometers (11 mi) (about 11 miles) long because it has many braided sections.

In Kiama, Australia, there's a system with over 20 lava tubes. The biggest one is 2 meters (6.6 ft) (about 6.5 feet) wide and has cool patterns on its walls from how the lava cooled.

Lava Tubes on Other Planets

Scientists have found lava tubes on the Moon and Mars!

• Lunar lava tubes: These have been discovered on the Moon. Scientists are studying them because they could be good places for humans to live in the future. They would offer natural protection from harmful radiation from space.
• Martian lava tubes: On Mars, many lava flows and channels have lava tubes. Sometimes, parts of these tubes have collapsed, creating chains of pit craters that you can see from space. Scientists also think that lava coming out of intact underground tubes formed large, fan-shaped areas.

Caves, including lava tubes, are interesting places to look for signs of life beyond Earth.

Famous Lava Tubes

Here are some well-known lava tubes around the world:

• Iceland
  • Surtshellir – For a long time, this was known as the longest lava tube in the world.
• Kenya
  • Leviathan Cave – At 12.5 kilometers (about 7.8 miles), it's the longest lava tube in Africa.
• South Korea
  • Manjang Cave – More than 8 kilometers (about 5 miles) long, located on Jeju Island, and a popular place for tourists to visit.
• United States
  • Kazumura Cave, Hawaii – This is not only the most extensive lava tube in the world, but at 65.5 kilometres (40.7 mi) (about 65.5 kilometers), it's the longest known cave of any kind!

Images for kids

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  Valentine Cave, a lava tube in Lava Beds National Monument, California. You can see its classic tube shape and grooves on the wall from past lava levels.

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  Thurston Lava Tube in Hawaii Volcanoes National Park, Hawaii. The step mark on the right wall shows how deep the lava flowed for a while.

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  Rare features in lava tubes are lava pillars. This is the Manjanggul lava pillar in the Manjanggul lava tubes, on Jeju-do, Korea.

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  Lavacicles hanging from the ceiling of Mushpot Cave in Lava Beds National Monument.

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  A close-up of a skylight (a hole in the roof) on a coastal plain, with lava stalactites forming inside the tube, Hawaii Volcanoes National Park.

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  The entrance of a lava tube on the Big Island, Hawaii.

See also

In Spanish: Tubo de lava para niños

• Caving
• Geology of the Moon
• Lava cave
• Mars habitat
• Speleology
• Speleothem