Difference Between Lava and Magma

The key difference between lava and magma is that lava is the hot mixture of gases and molten rocks that come out of the volcano whereas magma is the molten rock material deep inside earth’s crust.

Hence, the difference between lava and magma pertains to their location. Well, before going into a discussion about this difference, let us see what each term refers to. Not many of us know that the temperature beneath the surface of the earth increases as we go down. In fact, the temperature at the center or core is so high that it consists of nothing but molten rocks and other solid materials because of extremely high temperatures. This mixture of molten rocks is magma. This magma resides in certain places; chambers that have passages up to volcanoes. When volcanoes erupt, it is this magma that constantly comes out of the volcanoes. When this magma comes out of volcanoes, we call it lava.

CONTENTS

1. Overview and Key Difference
2. What is Lava
3. What is Magma
4. Side by Side Comparison – Lava vs Magma in Tabular Form
5. Summary

What is Lava?

Lava is also molten rock. When the magma that has been gathering under the earth’s crust comes out of a volcano, it is termed as Lava. There are different types of lavas that are classified according to their consistencies or viscosity. Lava that is thin can flow downhill for kilometers and makes a gentle flow or slope. Thick lava finds it difficult to flow, and the thickest lava does not even flow and plugs up the mouth of a volcano, causing great explosions in future. Let us see what the different types of lava are. There are three main types of lava. They are A’a, Pahoehoe, and Pillow Lava.

Lava composition: Lava contains mainly silicate minerals such as;

• Feldspar
• Olivine
• Pyroxenes
• Amphiboles
• Micas
• Quartz

A’a is the first type of lava, and it is pronounced as ‘ah-ah.’ This type of lava does not flow very quickly. It will look like a slow moving mass of lava with a hard surface. Once this lava hardens, it is very hard for anyone to walk on that surface. Then, there is Pahoehoe lava. This name is pronounced as pa-ho-ho. This type of lava can easily flow down the slopes because the viscosity is lesser than A’a lava. Finally, we have Pillow Lava. This type of lava you get to see when an underwater volcano erupts. Just like hot water, when this hot lava meets with the cool water, it automatically cools down and forms a kind of a hard shell. When more lava comes from the volcano mouth, the shell cracks and more pillow like hard surfaces are built.

What is Magma?

Lava is the hot mixture of gases and molten rocks that come out of the volcano. Magma, as we discussed earlier, is molten rock. We stand on the cool earth, and cannot even think or imagine how hot down there at the center of the earth. As one travels down the crust and enters the mantle, the temperature gradually increases, and there are pockets of mantle where one can find molten rock. This molten rock, called magma, finds its way up to the surface of the earth through fissures and cracks and also through chambers that fed into volcanoes.

The earth’s crust is made up of plates that keep on colliding with each other. Normally, these plates fit together like pieces of a huge jigsaw puzzle, but when they move, they cause friction and release of lots of energy. When plates collide, one section slide over another, and the one beneath is pushed down. This causes molten rock or magma to squeeze up between the plates. For those who think of volcanoes as fury of nature, they are actually giant safety valves that release the pressure that builds up because of high temperatures inside the earth. The magma that reaches the mouth of the volcano is around 700-1300 degrees Celsius.

Sources of Magma:

• Partial melting of mantle rocks for basalts, typically at a depth of 70-100 km
• Partial melting of continental rock for rhyolites

Depending on their chemical composition, there are three types of magma as well. They are Basaltic magma, Andesitic magma, and Rhyolitic magma. Basaltic magma is low in K and Na and high in Fe, Mg and Ca. Andesitic magma is intermediate in Fe, Mg, Ca, K and Na. Rhyolitic magma is high in K and Na and low in Fe, Mg and Ca.

What is the Difference Between Lava and Magma?

Summary – Lava vs Magma

Lava and magma refer to the same compound. These two terms differ from each other based on the location and behavior of the compound. The difference between lava and magma is that lava is the hot mixture of gases and molten rocks that come out of the volcano whereas magma is the molten rock material deep inside earth’s crust.

Reference:

1. “Lava.” Wikipedia, Wikimedia Foundation, 4 May 2018. Available here 
2. “Magma.” Northern Europe. Available here 

Image Courtesy:

1.’Pahoehoe toe’By Hawaii Volcano Observatory (DAS) (Public Domain) via Commons Wikimedia  
2.’67574′(Public Domain) via Max Pixel