Lava tube

Hot melted rock flows from a volcano.

The top of the flow cools down. It becomes a hard roof. The hot rock stays inside. It flows like a river under the roof.

Later, the hot rock drains away. This leaves an empty cave. You might see small rock drips on the ceiling.

These drips are very common. These caves can be very long. They can even be found on the moon!

A lava tube is a natural cave.

It forms when hot, melted rock flows from a volcano. This rock is called lava. As the lava flows, the outside cools down. It forms a hard crust or roof. The hot lava stays inside the tube. It can flow much further than regular lava flows. This happens because the crust protects the heat.

Lava tubes can form in a few ways. Sometimes, the sides of a lava channel cool first. These sides are called levees. If the lava stays at one level, a roof forms. If the level changes, the levees can grow together. Other times, the pressure of the lava makes the flow swell up. This is called inflation.

When the lava stops flowing, it drains away. This leaves an empty cave. You might see small rock drips on the ceiling. We call these lavacicles.

These are the most common things to find inside. Some tubes are very long. Scientists think people could live in tubes on the Moon. The thick roof would protect people from space radiation.

A lava tube is a natural, roofed path for molten lava.

These tubes are very important for volcanoes. They can carry hot lava much further away from a volcanic vent. This happens because a solid crust forms on top. This crust acts like a protective blanket. It keeps the heat inside and stops the air from cooling the lava too fast. Because of this, lava tubes help move molten rock long distances.

There are a few ways these tubes form. First, lava flows in a channel. The sides cool quickly and form walls called levees. If the lava level stays the same, a crust forms from the walls toward the middle. If the level changes, the levees grow and join together to make a roof. Sometimes, the pressure of the lava makes the flow swell up. This is called inflation. As the surface cools, it creates a hard crust over the moving lava.

When the lava stops flowing, it drains away. This leaves an empty cave behind. You might see many interesting features inside these caves. Wall linings form when the tube drains and refills. Step marks, or lava benches, show how deep the lava once was. You might also see lavacicles on the ceiling. These are small lava stalactites. They are the most common feature found inside.

Some tubes even have lava pillars or drips called stalagmites.

Lava tubes come in many different sizes and shapes. Some are narrow, while others are very wide. The Kazumura Cave in Hawaii is the world's most extensive lava tube. It is 6.4 kilometers long. In South Korea, Manjang Cave is more than 7 kilometers long. This cave is a popular place for tourists to visit.

There is also a system in Kiama, Australia. It has over 20 tubes. The largest one there is very wide. It has special patterns called columnar jointing on its walls.

Scientists even look for lava tubes in space. On the Moon, tubes could be homes for humans. The thick rock would provide shielding from radiation. On Mars, lava tubes are linked to many lava flows. They are found near Olympus Mons and in the Tharsis region.

These tubes are also places where scientists look for signs of life. Studying these caves helps us understand how planets work. It is amazing to think that a cave on Earth could be like a home on the Moon.

A lava tube is a natural, roofed conduit used by molten lava.

These structures are sometimes called pyroducts or lava tunnels. They are very important in volcanic systems. Lava tubes allow molten rock to travel much further from an eruptive vent than simple lava channels. This happens because a solid crust forms on top of the flow. This crust protects the molten lava from atmospheric cooling. Because the heat is trapped inside, the lava can travel over long distances.

Scientists use these features when they create hazard maps. They also consider lava tubes when managing an eruptive crisis.

Lava tubes form through several specific mechanisms. The first method is the roofing of a lava channel. When lava erupts, it usually flows in channels. The core of the channel stays very hot. However, the sides cool rapidly and form solidified walls called levees. If the lava level stays stable, a crust forms from the levees toward the center. If the level is irregular, lava overspills the levees. These levees eventually grow and join together to form a roof. A second method is pāhoehoe lobe extension. This occurs when aligned lobes of pāhoehoe lava are continuously fed by molten lava. A third method is lava flow inflation. In this case, the pressure of the molten lava causes the flow to swell. The surface solidifies as it cools, creating a crust that forms a tube.

Lava tube systems can be quite complex. A broad lava-flow field often contains a main tube. This main tube is connected to smaller tubes. These smaller tubes supply lava to the front of separate flows. When an eruption ends or lava is diverted, the liquid drains away. This leaves behind partially or fully empty caves. These drained tubes contain many internal features. These features tell scientists about the activity that happened inside the tube.

These features include wall linings, which are thin layers of lava. These linings form during cycles of drainage and refilling.

Many distinct shapes and structures exist inside these caves. Step marks on the walls are very common. These are also called lava benches, flow ledges, or flow lines. They indicate the different depths at which the lava once flowed. The floors are generally made of pāhoehoe lava. However, they are often covered in breakdown from the ceiling. One of the most common features is the lavacicle. These are lava stalactites found on the ceiling. They can be splash, "shark tooth," or tubular varieties.

You might also find drip stalagmites under tubular lavacicles. Some stalagmites may even have a central conduit. These are interpreted as hornitos that extruded from the tube floor.

Lava tubes vary greatly in size and location. They can be narrow or extremely wide. They can run just below the surface or deep underground. Some tubes are incredibly long. One tube from the 1859 Mauna Loa flow enters the ocean. The Cueva del Viento–Sobrado system on Tenerife is also very long. It has extensive braided maze areas in its upper zones. In Kiama, Australia, a system consists of over 20 tubes. The largest tube there has columnar jointing on its walls. This happens because of the large cooling surface.

Other tubes in that system show concentric and radial jointing.

There are many famous examples of these caves around the world. In Iceland, Surtshellir was once the longest known lava tube. Italy has the Grotta dei Tre Livelli, which is a multiple-level tube. Kenya is home to Leviathan Cave, the longest in Africa. In South Korea, Manjang Cave is more than 7 kilometers long. It is a popular spot for tourism. The most extensive system is Kazumura Cave in Hawaii. It is 6.4 kilometers long and has a massive linear extent. These sites help us understand how volcanic landscapes are built.

Scientists are also studying lava tubes on other worlds. Lunar lava tubes have been discovered on the Moon. These could serve as human habitats. The rock provides natural shielding from radiation. On Mars, lava tubes are linked to many lava flows. They are found near Olympus Mons and the Tharsis region. Some tubes appear as chains of pit craters. Others form broad lava fans. These caves are also considered candidate biotopes. This means they are interesting places to look for extraterrestrial life.