Magma and Lava: Important Facts, Types, Differences & More

The oldest fluid found on the earth is known as Magma. It is a combination of silicates, oxides, and other volatile components. A magnetic chamber under the earth’s crust holds the magma. When magma attains the surface through cracks and fissures in the rocks, it erupts as lava. The words magma and lava have their origins in Latin and Greek, respectively. Lava originates from the Latin word ‘labes,’ which refers to a fall or a slide. The term magma originates from the Greek word ‘magma,’ which refers to a thick unguent.’ An unguent is a dense paste that is utilized in treating injuries to the skin. The term "magma" is employed by scientists to refer to molten rock located beneath the Earth's surface, while "lava" is used to describe molten rock that erupts and emerges on the Earth's surface.

Magma and Lava is one of the most important topics for the UPSC IAS exam. It covers a significant part of the Geography subject in the General Studies Paper-1 syllabus and General Studies paper 1 of the UPSC Prelims syllabus.

In this article prepared by the Testbook UPSC Online Coaching team, let us look at what is magma and lava, the origin of magma and lava, their types, important facts, similarities and differences between magma and lava for the UPSC IAS Examination in detail.

What is Magma?

Magma is the molten or semi-molten rock or volatile matter that is found under the surface of the earth. This vicious or molten rock resides in the magma chamber underneath a volcano or hardens underground to form an intrusion. The magma either fills up the fissures in rocks or comes out of volcanoes in eruptions. Certain mechanisms of magma formation in the mantle are decompression melting, heating, and lowering of the solidus.

What is Lava?

Magma, on reaching the surface and breaking out of a volcano, is officially termed lava. It is a semi-solid, burning-hot material. It reaches the surface via a volcano duct or vent. When initially exuded from a volcanic opening, the hot lava is at temperatures ranging from 700 °C to 1,200 °C.

Difference Between Lava and Magma

Here we will discuss the difference between magma and lava:

Difference Between Magma and Lava
Parameter of Comparison	Magma	Lava
Definition	The molten rock matter that is present under the surface of the earth is known as magma.	The molten liquid matter that gets erupted out of the surface of the earth is known as lava. Lava is also known as liquid magma.
Temperature	The temperature possessed by magma is slightly higher and it varies from 1300-2400 degrees Fahrenheit.	The temperature possessed by lava is slightly lesser and it varies from 1300-2200 degrees Fahrenheit.
Period of Cooling	Magma takes a longer time to cool down since it is situated under the Earth’s surface which results in the creation of gigantic crystals.	Lava takes comparatively a lesser time to cool down than magma. At times, this results in lava crystallizing into glass.
Location	Magma is located below the Earth’s crust.	Magma is termed lava only when it reaches the Earth’s surface.
Flow Characteristics	It does not flow due to the confined space and high pressure in the magma chambers.	It is free to flow on the surface of the earth resulting in severe damage to the property and the lives of humans.
Composition	It is a mixture of minerals and small quantities of dissolved gasses like carbon dioxide, sulfur, etc.	Lava is a combination of slush of crystals, fluid and bubbles. It also consists of chemical elements.
Origin of the Terminology	The term magma has an ancient Greek origin.	The term lava has its origins in the Italian language.

Origin Of Magma

• All magma forms through the fusing of pre-existing rocks. Usually, this takes place in one of the below two ways:
  • By convection of rock upwards through the mantle till it melts, or
  • By melting rocks at a subduction zone.
• Mantle convection happens since deep inside the earth, radioactive decomposition increases the temperature of rock, causing it to expand. This expansion reduces the rock’s density, causing it to rise or convect.
• As the rock rises via the mantle, the adjacent pressure decreases, and finally, the convecting rock melts. This is called pressure-relief melting.
• The magma moves upward and breaks out to form either an oceanic ridge or a hot spot volcano.
• At subduction zones, volatile matter (particularly water) escapes from the subducting plate and lower the melting temperature of the overlying mantle rocks. This initiates melting, and magma forms as a result.
• As magma rises in the mantle and crust, it is subjected to fractional crystallization. Each mineral in a rock possesses its crystallization temperature. Since various minerals crystallize at various temperatures, some minerals form from magma earlier than others. Hence, the minerals that crystallize later and the rocks that they form will be of a varied composition than those that form earlier.
• If a rock is not exposed to a high enough temperature to fuse all of its minerals, only some minerals will melt. This is termed partial melting. If a rock melts partially, the magma developed will have a varied chemical composition than the rock from which the magma emerged.

Also read: NCERT notes on Earthquake

Origin Of Lava

• Lava is a molten rock mass that is formed deep under the earth’s surface, where temperatures get hot enough to fuse rock. This fluid-rock is called magma when it’s underground.
• Eventually, some magma reaches the earth’s surface and flows out via a volcanic outbreak. When magma erupts on the earth’s surface and starts to flow, it is termed lava. This magma, which is termed lava when it attains the surface of the earth, is largely made up of basalt, which hardens and then forms a layer on top of a layer of lava.
• Explosive outbreaks can throw lava to great distances. Most eruptions, however, generate slow-moving lava flows that cover just a few yards per minute.

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Different Types of Magmas

Usually, the magmas are classified into four different types:

• Ultramafic Magma
• Mafic Magma
• Intermediate Magma
• Felsic Magma

We will explain these types in detail below:

Ultramafic Magma

• The ultramafic magma attains temperatures of about 1500 degrees Celcius.
• It has a very low viscosity (which results in milder and less explosive eruptions).
• It is distributed throughout divergent plate boundaries, hot spots, and convergent plate boundaries.

Mafic Magma

• The mafic magma attains temperatures of about 1300 degrees Celsius.
• This type of magma also possesses a low viscosity.
• It has mild eruptions.
• It is also distributed across divergent plate boundaries, hot spots, and convergent plate boundaries.

Intermediate Magma

• The intermediate magma attains temperatures of about 1200 degrees Celcius.
• The viscosity of this is intermediate.
• It has explosive or gushing eruptions.
• It is distributed throughout convergent plate boundaries and island arcs.

Felsic Magma

• The felsic magma attains temperatures lesser than 900 degrees Celcius.
• It is extremely viscous.
• The eruptions are explosive.
• It is commonly distributed in hot spots in the continental crust and rifts.

Based on density, the magmas are categorized into the following three types:

• Basalt Magma
• Andesite Magma and
• Rhyolite Magma

Different Types of Lava

Silicate lava is generally classified into five types:

• Felsic Lava
• Intermediate Lava
• Mafic Lava
• Ultramafic Lava
• Alkaline Lava

We will get detailed information about these types below:

Felsic Lava

• These are also called silicic lava.
• The silica content of the felsic lava is more than 60%.
• The felsic lava possesses extreme viscosity.
• On the eruption of felsic lava, pyroclastic deposits are formed.

Intermediate Lava

• Intermediate lava is also termed andesitic lava.
• The silica content in the intermediate lava ranges between 52% and 63%.
• These types of lava generally occur on steep composite volcanoes.
• The temperature changes from 850 degrees celsius to 1100 degrees Celsius.
• It has a low viscosity.
• Upon eruption, they form phenocrysts.

Mafic Lava

• They are also termed basaltic lava.
• The silica content in the mafic lava ranges between 45% and 53%.
• The viscosity of mafic lava is comparatively low.
• The mafic lava creates shield volcanoes or flood basalts.

Ultramafic Lava

• The silica content of ultramafic lava is lower than 45%.
• Komatite and Boninite are some examples of ultramafic lava.

Alkaline Lava

• These are a form of silicic lava with an elevated content of alkali metal oxides.
• The silica matter present in alkaline lava is that contained between ferric lava and ultramafic lava.

Know about NCERT notes structure of atmosphere here.

Facts about Magma

The extremely hot semi-liquid and liquid rock matter present in the earth’s crust is known as Magma. In addition, the planet Earth consists of several layers, notably – the inner core, outer core, mantle, and crust. The magma is substantially present in the earth’s mantle. Magma generally contains itself inside magma chambers. These chambers generally hold a collection of dissolved gasses, suspended crystals, and gas bubbles. However, this molten substance propels through cracks and fissures in the exterior surface, which results in a volcanic emission. A few related highlights of magma are as follows-

• Magma is made up of minerals.
• It contains dissolved gasses like carbon dioxide, water vapour, and Sulphur in low amounts.
• Magma remains in a liquid state due to high pressure and utmost temperature below the earth’s crust.
• The heat that is generated within magma ranges from a temperature of about 1300 to 2400 degrees.
• Magma is categorized into three main types, namely basaltic, rhyolitic, and andesitic, and each of these types has a specific composition of minerals.
• Silicon dioxide is present in a substantial quantity in all types of magma.

Facts about Lavas

The molten rock matter, when it attains the surface of the earth, it turns into lava. It has a temperature that ranges from 700 °C to 1200 °C (which is 1300 °F to 2200 °F). In addition, the material of lava can be completely free-flowing, similar to fluids. But, it can also be very rigid. Lava is usually classified based on a number of factors, such as the viscosity and composition of the lava that spews out. A few highlights related to lava are as follows:

• The larger the amount of silica present in lava, the higher its viscosity (thickness).
• Lava is a combination of silicate minerals like olivine, amphibole, quartz, mica, feldspar, and pyroxene.
• The above-mentioned composition exhibits the behaviour of lava rather than its temperature during an eruption.
• Lava flow can be categorized into three basic types – Aa lava flow, pahoehoe lava flow, and blocky lava flow. The Aa flow consists of free lumps of sharp lava pieces, while pahoehoe flow is comparatively smooth. On the other hand, blocky flow is more or less comparable to Aa flow. But it is relatively more viscous.

Check NCERT notes on Earth – Origin & Evolution here.

Similarities Between Magma and Lava

• Composition: Both magma and lava are primarily composed of molten rock, which consists of various minerals and elements, including silica, iron, magnesium, and others.
• Temperature: Magma and lava are extremely hot substances, with temperatures typically ranging from 700 to 1,300 degrees Celsius (1,292 to 2,372 degrees Fahrenheit).
• Movement: Both can flow and move, driven by the force of pressure and buoyancy, as well as the influence of gravity.
• Origin: Magma is the precursor to lava. It forms beneath the Earth's surface through the melting of rock due to high temperatures and pressure. When it erupts and reaches the Earth's surface, it becomes lava.
• Role in Volcanic Activity: Both magma and lava play crucial roles in volcanic eruptions. Magma rises to the surface during an eruption, leading to the release of gases and the formation of volcanic landforms.
• Chemical Composition Variation: The composition of both magma and lava can vary widely, leading to differences in their behavior and the types of volcanic eruptions they produce (e.g., explosive or effusive).
• Cooling and Solidification: As both magma and lava cool and lose heat, they solidify to form igneous rocks. The rate of cooling and the specific mineral content determine the type of igneous rock that forms.

Also read: What is Tsunami? here for UPSC Geography Preparation.

Conclusion

Magma and Lava are both molten rocks possessing varied compositions. Magma is made up of silicon dioxide, aluminium oxide and potassium oxide. Lava is made up of silicon dioxide and magnesium oxide. The temperatures at which magma and lava harden also vary; magma crystallizes at a temperature of 1,200 degrees Celsius, whereas lava crystallizes at a temperature of 950 degrees Celsius. These variations account for the different physical properties of these two types of molten rock.

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