Lava is molten rock that emerges as a liquid onto Earth’s surface. It is also the term for the solidified rock formed after the lava cools. Temperatures of lava range from 700 to 1,200 °C (1,300 to 2,200 °F). The chemical composition of magma affects its physical properties, influencing the landform that a volcanic eruption builds. As silica content increases, rock types generally become more viscous and, as the magmatic gas content increases, they become more explosive. There are two major types of lava flow: * Pahoehoe, a fluid flow with a smooth or ropy surface. * Aa, a viscous flow with a surface covered by sharp, loose blocks.

How does lava reach the Earth's surface?

Magma forms 40 to 120 miles below Earth's surface where temperatures are high enough to melt rock. Because it is less dense than the surrounding solid rock, magma rises towards the surface due to gravity. In some instances, magma moves directly to the surface through fissures, especially in undersea zones where tectonic plates separate. In other cases, it accumulates in magma chambers before erupting. Molten rock that emerges onto Earth’s surface is called lava .

What are the main types of lava?

Lava is magma that reaches Earth's surface. There are different types of lava, including: Pahoehoe: Fluid lava with a smooth or ropy surface Aa: Viscous lava with a surface covered in loose, sharp blocks Block Lava: Lava flows of andesitic or intermediate composition that have fragments that are more regular in shape Pillow Lava: Pillow-shaped masses that form underwater when fluid lava is quenched by the surrounding water The viscosity of lava, or its resistance to flow, is affected by its temperature, chemical composition, and gas content. The higher the silica content, the higher the viscosity.

How does lava shape the landscape after a volcanic eruption?

After a volcanic eruption, lava shapes the landscape in several ways. The volume of volcanic products, the interval length between eruptions, the composition of volcanic products, the variety of volcanic eruption types, the geometry of the vent, and the environment into which the volcanic products are erupted all contribute to the size and shape of a volcano. Effusive eruptions create lava plateaus or gently sloping shield volcanoes. In contrast, explosive eruptions form stratovolcanoes, and giant explosive eruptions form plateaus of lava or ash flows and calderas. There are two major types of lava flows: pahoehoe , which has a smooth or ropy surface, and aa , which has a surface covered by thick, jumbled piles of loose, sharp blocks. Over time, the decomposition of nutrient-rich volcanic fallout creates fertile soils. Lava flows can also solidify to create lava caves .

What is the difference between lava and magma?

The terms magma and lava both refer to molten rock, but they are not interchangeable. Magma is molten rock beneath the Earth's surface, while lava is magma that has erupted onto the Earth's surface. Lava flows are the most common product of volcanoes. After reaching the surface, lava cools and solidifies, forming various types of volcanic rock.

What other materials, besides lava, are ejected during a volcanic eruption?

Volcanic eruptions eject various materials in addition to lava. These include toxic gas clouds composed of water vapor, carbon dioxide, sulfur dioxide, and hydrogen sulfide. Solid materials are also ejected, classified by size as volcanic dust, volcanic ash, cinders (or scoriae), blocks, and volcanic bombs . Pyroclastic flows, which are fluidized mixtures of hot rock fragments, hot gases, and entrapped air, can also occur. Pumice, a porous volcanic glass, is another material that can be ejected during eruptions.

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Introduction References & Edit History Related Topics

Images & Videos

Study how magma erupts as lava and turns into pumice or hardens to form a shield volcano

View lava erupting from a submarine vent near the Mariana Islands

The stages of lava: From eruption to cooling

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Lava flows from the eruption of the Mauna Loa volcano on the island of Hawaii, March 25, 1984

Quick Facts

Related Topics:: basaltic lava; block lava flow; pahoehoe; pillow lava; lava flow

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volcanic ejecta

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Sep. 26, 2026 •History

Top Questions

What is lava?
Lava is molten rock that emerges as a liquid onto Earth’s surface. It is also the term for the solidified rock formed after the lava cools. Temperatures of lava range from 700 to 1,200 °C (1,300 to 2,200 °F).

The chemical composition of magma affects its physical properties, influencing the landform that a volcanic eruption builds. As silica content increases, rock types generally become more viscous and, as the magmatic gas content increases, they become more explosive.

There are two major types of lava flow:
* Pahoehoe, a fluid flow with a smooth or ropy surface.
* Aa, a viscous flow with a surface covered by sharp, loose blocks.
3 Britannica Sources
Created from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.
How does lava reach the Earth's surface?
Magma forms 40 to 120 miles below Earth's surface where temperatures are high enough to melt rock. Because it is less dense than the surrounding solid rock, magma rises towards the surface due to gravity. In some instances, magma moves directly to the surface through fissures, especially in undersea zones where tectonic plates separate. In other cases, it accumulates in magma chambers before erupting. Molten rock that emerges onto Earth’s surface is called lava.
3 Britannica Sources
Created from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.
What are the main types of lava?
Lava is magma that reaches Earth's surface. There are different types of lava, including:
- Pahoehoe: Fluid lava with a smooth or ropy surface
- Aa: Viscous lava with a surface covered in loose, sharp blocks
- Block Lava: Lava flows of andesitic or intermediate composition that have fragments that are more regular in shape
- Pillow Lava: Pillow-shaped masses that form underwater when fluid lava is quenched by the surrounding water
The viscosity of lava, or its resistance to flow, is affected by its temperature, chemical composition, and gas content. The higher the silica content, the higher the viscosity.
6 Britannica Sources
Created from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.
How does lava shape the landscape after a volcanic eruption?
After a volcanic eruption, lava shapes the landscape in several ways. The volume of volcanic products, the interval length between eruptions, the composition of volcanic products, the variety of volcanic eruption types, the geometry of the vent, and the environment into which the volcanic products are erupted all contribute to the size and shape of a volcano.

Effusive eruptions create lava plateaus or gently sloping shield volcanoes. In contrast, explosive eruptions form stratovolcanoes, and giant explosive eruptions form plateaus of lava or ash flows and calderas.

There are two major types of lava flows: pahoehoe, which has a smooth or ropy surface, and aa, which has a surface covered by thick, jumbled piles of loose, sharp blocks. Over time, the decomposition of nutrient-rich volcanic fallout creates fertile soils. Lava flows can also solidify to create lava caves.
3 Britannica Sources
Created from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.
What is the difference between lava and magma?
The terms magma and lava both refer to molten rock, but they are not interchangeable. Magma is molten rock beneath the Earth's surface, while lava is magma that has erupted onto the Earth's surface.

Lava flows are the most common product of volcanoes. After reaching the surface, lava cools and solidifies, forming various types of volcanic rock.
5 Britannica Sources
Created from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.
What other materials, besides lava, are ejected during a volcanic eruption?
Volcanic eruptions eject various materials in addition to lava. These include toxic gas clouds composed of water vapor, carbon dioxide, sulfur dioxide, and hydrogen sulfide.

Solid materials are also ejected, classified by size as volcanic dust, volcanic ash, cinders (or scoriae), blocks, and volcanic bombs. Pyroclastic flows, which are fluidized mixtures of hot rock fragments, hot gases, and entrapped air, can also occur. Pumice, a porous volcanic glass, is another material that can be ejected during eruptions.
4 Britannica Sources
Created from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.

lava, magma (molten rock) emerging as a liquid onto Earth’s surface. The term lava is also used for the solidified rock formed by the cooling of a molten lava flow. The temperatures of molten lava range from about 700 to 1,200 °C (1,300 to 2,200 °F). The material can be very fluid, flowing almost like syrup, or it can be extremely stiff, scarcely flowing at all. The higher the lava’s silica content, the higher its viscosity.

pahoehoePahoehoe lava flow, Kilauea volcano, Hawaii, November 1985. Pahoehoe lava flows are characterized by smooth, gently undulating, or broadly hummocky surfaces.

Mafic (ferromagnesian, dark-coloured) lavas such as basalt characteristically form flows known by the Hawaiian names pahoehoe and aa (or a’a). Pahoehoe lava flows are characterized by smooth, gently undulating, or broadly hummocky surfaces. The liquid lava flowing beneath a thin, still-plastic crust drags and wrinkles it into tapestry-like folds and rolls resembling twisted rope. Pahoehoe lava flows are fed almost wholly internally by streams of liquid lava flowing beneath a solidified or partly solidified surface. Typically, the margin of a pahoehoe flow advances by protruding one small toe or lobe after another.

In contrast to pahoehoe, the surface of aa lava is exceedingly rough, covered with a layer of partly loose, very irregular fragments commonly called clinkers. Aa lava flows are fed principally by rivers of liquid lava flowing in open channels. Typically, such a feeding river forms a narrow band that is 8 to 15 metres (25 to 50 feet) wide along the centre line of the flow, with broad fields of less actively moving clinker on each side of it. At the front of the flow, clinkers from the top roll down and are overridden by the pasty centre layer, like a tread on an advancing bulldozer.

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