Difference between Volcano Magma and Volcano Lava

The Difference
Magma: The partially or fully molten rock found below the Earth's surface.

Lava: The molten rock that flows out to reach the Earth's surface.

Before understanding the terms 'magma' and 'lava' that are associated with volcanoes, let us revise how volcanoes are formed and what causes volcanic eruptions. Certain temperature and pressure conditions arising in the Earth's crust, cause its floating plates to move and collide with each other, resulting in the formation of a volcano.

The rising molten magma, causes a volcano to erupt. It is untrue that volcanoes erupt only on land. Volcanoes can be present under water or even under snow. There are gaps in the Earth's crust that serve as vents for the molten magma to erupt to the Earth's surface.

What is volcano magma? How is it different from volcanic lava? By definition, the molten rock in the Earth's crust is known as magma. It originates several miles below the Earth's surface and ascends outward. It contains crystals, fragments of rocks from the surrounding region and dissolved gases.

Volcano magma also consists of oxygen, silicon, aluminium, magnesium, calcium, iron, sodium, potassium and manganese, and many other elements in smaller quantities. This is the reason why magma, on solidification, precipitates crystals of various minerals.

While magma is molten rock lying below the surface of the Earth; lava is the red-hot liquid that pours out of the vent in the Earth's crust onto its surface. Lava is fairly similar to magma in its chemical composition. It is made of crystals, liquid, and bubbles.

It contains minerals like silicon, sodium, potassium, calcium, phosphorus, and traces of many other elements. If the lava is not viscous, the gases dissolved in it can escape easily. However, if the lava is highly viscous, the gases cannot move freely and they build up pressure until they escape with an explosion.

Fresh lava has a temperature of about 700 to 1200 degrees Celsius and glows red-hot as it flows. Interestingly, volcano lava freezes to form a substance containing a high concentration of silica, and is known as volcanic glass.

How are magma and lava interrelated? Well, if the magma contains a high percentage of silica, the lava is felsic. Felsic lava is viscous and tends to form lava domes.

Highly viscous lavas lead to a violent eruption. If the erupted magma contains about 50-60% silica, the lava is said to have an intermediate composition.

If the erupted magma contains about 45-52% silica, the lava is mafic or basaltic, which means that it contains higher amounts of magnesium and iron. Mafic lavas are less viscous and generally hotter than felsic lavas.

Both magma and lava are molten rock. The only difference is that magma is under the pressure of the Earth's crust; while the lava is above the ground. Therefore, lava flows freely; its flow depends on its viscosity. Thus we see, that magma and lava differ in their physical characteristics, though their chemical composition is almost the same.

Lava is, in fact, the volcanic magma which reaches the Earth's surface. The red-hot lava that spews out from beneath the Earth, is the magma that for many years, had been waiting to make a fierce exit onto the Earth's surface. Names change, nature does not!