Lava

Lava is melted rock.

It comes from deep inside the Earth. It can come out of a volcano. It can also come from cracks in the ground.

Lava can flow on land. It can also flow under the sea. Some lava is thick like ketchup. Other lava is thin like oil.

When lava hits the air, it forms a crust. This crust stays hard on top. It keeps the inside hot. This helps the lava keep moving.

Lava can even fly into the air. It can fall back down to the ground. When it cools, it turns into solid rock.

Lava is a very amazing thing to see.

Lava is melted rock. It comes from deep inside a planet. It can come out of a volcano. It can also come from cracks in the ground.

Lava can flow on land or under the sea. It can even be thrown into the air. When it cools, it becomes solid rock.

How lava moves depends on its viscosity. Viscosity is how thick a liquid is. Some lava is thick like ketchup. This is called mafic lava. It can flow for a long way. It often makes wide, gentle volcanoes.

Other lava is very thick. It is called felsic lava. This type has a lot of silica. Silica is a mineral found in the Earth's crust. Felsic lava does not flow easily. It often erupts in an explosive way.

Some lava is like smooth peanut butter. We call this intermediate lava.

When lava hits the air, it forms a crust. This crust acts like a blanket. It keeps the liquid inside hot. This helps the lava keep moving.

Lava is molten rock that comes from inside a planet. It can erupt from a volcano or through a crack in the Earth's crust. This can happen on land or even deep underwater. Sometimes, it is even thrown into the air before it falls back down. When this hot liquid cools, it turns into solid volcanic rock.

This process is very important for making new land on Earth.

How lava moves depends on its viscosity, which is how thick a liquid is. Most lava is like ketchup, which is much thicker than water. Even though it is thick, lava can flow very far. This happens because the air creates a solid crust on the outside. This crust acts like a blanket to keep the inside hot. The heat helps the liquid stay thin enough to keep flowing.

Scientists group lava into four main types based on how much silica it has. Silica is a mineral made of silicon and oxygen. Felsic lava has more than 63% silica and is extremely thick. It often erupts in explosive ways. Intermediate lava has 52% to 63% silica and is like smooth peanut butter.

Mafic lava has 45% to 52% silica and is much thinner. It can flow long distances to make shield volcanoes.

Finally, ultramafic lava has less than 45% silica and is very runny.

People have studied these flows for a long time. The word lava comes from the Italian language. It likely comes from a Latin word meaning flow. One early record of the word was in 1737. A writer named Francesco Serao described a flow from Mount Vesuvius. He compared the fiery lava to a flow of water and mud.

Lava can look very different depending on where it goes. If it flows into the ocean, it can form pillow lavas. On land, mafic lava can create smooth shapes called pāhoehoe.

It can also create rougher types called aā. Some thick lavas form steep domes or block flows.

These different shapes help us understand the history of our planet.

Lava is molten or partially molten rock that has moved from a planet's interior to its surface. This material, often called magma when it is underground, is expelled through volcanoes or fractures in the crust. It can erupt onto land or onto the sea floor. Sometimes, it is even ejected into the atmosphere before falling back down. Once the molten material cools, it becomes solid volcanic rock.

The way lava behaves is mostly determined by its viscosity. Viscosity is a measure of how thick a liquid is. Most molten lava has a viscosity similar to ketchup. This makes it about 10,000 to 100,000 times thicker than water. Despite this thickness, lava can flow great distances. When lava is exposed to air, it quickly develops a solid outer crust. This crust acts as an insulator for the liquid inside. It keeps the remaining lava hot and thin enough to continue flowing.

Most lavas on Earth are silicate lavas. These are molten mixtures dominated by oxygen and silicon. Silicon and oxygen are the most abundant elements in the Earth's crust. Other elements like aluminium, calcium, and magnesium are also present. The amount of silica determines the physical behavior of the melt. Silicon ions bind to oxygen ions in a tetrahedral arrangement. When oxygen ions connect two silicon ions, they are called bridging oxygens. This process is known as polymerization. High levels of polymerization make the lava more viscous.

Scientists divide silicate lavas into four chemical types based on silica content. Felsic lavas have a silica content greater than 63%. They include rhyolite and dacite and are extremely viscous. Because they are so thick, they often erupt explosively. They can also form lava domes or thick, short flows called coulees. Intermediate lavas contain between 52% and 63% silica. These are less viscous than felsic lavas and are similar to the thickness of smooth peanut butter.

Mafic lavas have a silica content between 45% and 52%. They are rich in magnesium and iron oxides. These lavas erupt at relatively low viscosities, similar to ketchup. Because they are thin, they can flow long distances to create shield volcanoes. On land, they often form pāhoehoe or aā types. Underwater, mafic lava can form pillow lavas. Finally, ultramafic lavas have less than 45% silica. They are extremely mobile because they have almost no polymerization. Most ultramafic lavas are no older than the Proterozoic era. The Earth's mantle has since cooled too much to produce them today.

History shows us how humans have observed these flows. The word lava comes from Italian and likely stems from a Latin word meaning flow. One early written account of lava comes from 1737. Francesco Serao wrote about the eruption of Mount Vesuvius. He described a flow of fiery lava by comparing it to water and mud.

This comparison helped people visualize the movement of molten rock.

Lava can also take very unusual forms. Some lavas are non-silicate. For example, carbonatite lavas are mostly carbonate minerals. The Ol Doinyo Lengai volcano in Tanzania is the only active carbonatite volcano. These lavas are extremely fluid and quite cool. Other rare types include iron oxide lavas and sulfur lava flows. Sulfur lavas can form at temperatures as low as 130 degrees Celsius.

These unique compositions show the incredible variety of geological processes on our planet.