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Gutenberg Discontinuity

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Gutenberg Discontinuity Definition

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The Gutenberg Discontinuity is situated inside the earth at a depth of about 2900 kilometres below the surface. The Gutenberg discontinuity separates the core and the mantle of the earth. Abundant, powerful forces reside below the earth's surface. These forces are responsible for triggering earthquakes, erupting lava through volcanoes, creating precious stones, and changing the landforms on the earth's surface from time to time, over the years. The structure of the earth has been a subject of study since ancient times. The Gutenberg discontinuity was named after Beno Guttenberg, who contributed several important facts and understanding of the earth's interior in 1913, which led to groundbreaking discoveries related to the inner layers of the earth.

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Discontinuities of the Earth Layers

The interiors of the earth are made of different kinds of elements that differ from each other in physical and chemical properties like temperature, density, composition, etc. The interiors of the earth are divided into separate layers. The fundamental layers of the earth are the crust, mantle, and core. These layers are further divided into the upper and lower crust, upper and lower mantle, and the outer and inner core. These layers are separated from each other by transition zones. These transition zones are popularly known as Discontinuities.

The various discontinuities of the earth are as follows-

  1. Conrad Discontinuity: 

The Conrad Discontinuity separates the upper and lower crust.

  1. Mohorovicic Discontinuity: 

This is the transition zone between the crust and the mantle.

  1. Repetti Discontinuity: 

This separates the upper mantle from the lower mantle.

  1. Gutenberg Discontinuity: 

This is the transition zone between the lower mantle and the outer core.

  1. Lehmann Discontinuity: 

This is the layer separating the outer core from the inner core.

The Weichert Gutenberg Discontinuity

Beno Gutenberg, a seismologist who studied the inner layers of the earth, observed that at a certain depth of the earth's surface, primary waves of earthquake slowed down dramatically. The secondary waves were stopped altogether. Secondary waves usually transmit entirely through a solid material but cannot travel through liquids. Hence, he concluded that at a specific depth at which the secondary waves of earthquakes vanish, there might be some liquid layer present. Seismic waves abruptly change at this liquid layer. This layer was called the Gutenberg Discontinuity. The layer is also called the Weichert-Gutenberg discontinuity or the Oldham-Gutenberg discontinuity.

The discontinuity proved that below this layer, the interior of the earth must be liquid, and above this layer, the interior of the earth would be solid. In reality, the outer core, which is below the Gutenberg discontinuity, is liquid with a much higher density than the mantle. It contains high quantities of iron. Below the outer core lies the inner core with densely packed iron and nickel. Above the Gutenberg Discontinuity lies the lower mantle, which is solid in nature but has a lower density than the outer core.

The Gutenberg discontinuity is narrow and uneven, with undulations extending up to 5-8kms width. The undulations often result from the underlying eddies and currents generated in the iron-rich outer core, which is the ultimate cause behind the magnetic field of the earth. The molten section below the discontinuity is 700°C hotter than the overlying mantle.

Shrinkage of the Core and Its Effect on the Gutenberg Discontinuity

The discontinuity between the mantle and the core is approximately 1800 miles below the earth's surface. However, this doesn't remain constant. The core of the planet experiences intense heat. This heat is perpetually and gradually dissipated, which forces the molten core to solidify and shrink slowly. The sinking of the core causes the Gutenberg discontinuity to sink deeper and deeper into the earth's surface gradually.

So, this is all about Mohorovicic discontinuity and Gutenberg Discontinuity. These discontinuities help in the study of the various interior layers of the earth. They give indirect information about the planet and assist in seismological studies.

Did You Know?

The discontinuities of the earth help in seismological studies. Seismology is the scientific study of earthquakes. The transition boundaries or the discontinuities of the earth give us information about the velocity of different earthquake waves in different layers of the earth, which helps us assess the nature of the layers of the earth.

FAQ (Frequently Asked Questions)

1. Differentiate between the Mohorovicic Discontinuity and the Gutenberg Discontinuity.

Ans: The differences between the Mohorovicic and Gutenberg Discontinuity are as follows-

Mohorovicic Discontinuity

Gutenberg Discontinuity

The Mohorovicic Discontinuity marks the transition zone between the crust and mantle.

Gutenberg Discontinuity marks the layer between the lower mantle and the outer core.

The Mohorovicic Discontinuity is located 8 kilometres below the ocean floor and 30-50 kilometres beneath the continents. 

The Gutenberg Discontinuity is situated at a distance of 2900 kilometres beneath the earth’s surface. 

It is named after Andriza Mohorovicic, who discovered it. 

It is named after Beno Gutenberg, who discovered it.

2. What do you mean by the terms Mohorovicic Gutenberg Lehmann?

Ans: These are names of the various discontinuities below the earth’s surface, which occur as transition zones between various layers of the earth. The interiors of the earth are divided into different layers depending upon its density, temperature, etc. These layers are separated from each other by transition zones known as discontinuities. The discontinuities mentioned above have the following features:


Mohorovicic Discontinuity: Situated between the crust and the mantle, the Mohorovicic Discontinuity separates both oceanic and continues talking crust from the underlying mantle. It lies mostly within the lithosphere. Beneath the mid-oceanic ridge, it defines the lithosphere and asthenosphere boundary.


Gutenberg Discontinuity: The Gutenberg Discontinuity is situated between the lower mantle and upper crust. It is this discontinuity at which the velocity of seismic waves changes abruptly. The S or shear seismic waves completely stop at this layer indicating that below this layer, the outer core is liquid in nature.


Lehmann Discontinuity: The Lehmann Discontinuity is the transition zone situated between the outer and inner core. There is an abrupt increase of seismic waves at this layer, indicating the fact that the inner core is solid.