The internal structure of the earth

Earth’s interior

We have always been curious to know about the interior of the Earth. The radius of our Earth is 6371 km. The interior of the Earth is studied in different layers.

If we talk about the chemical composition, the earth’s interior is classified into three layers: crust, mantle, and core.

interior of the earth, earth's interior, crust, mantle, core, lithosphere, asthenosphere

Based on the physical properties, the earth’s interior is divided into five layers:  lithosphere, asthenosphere, mesosphere, outer core, and inner core. Let’s talk about the crust, mantle, and core.


The crust is the very thin and outermost layer of the earth. The crust thickness varies between 0–75 km. Relative to the other layers, the crusts are rocky, cold, and brittle. There are two types of the earth’s crust: continental crust and oceanic crust

Continental crust is the outermost crust where mountain, soil, hill, river exists. The thickness of the continental crust is around 30 to 50 km. It is mostly composed of low-density crystalline rocks, where quartz and feldspar are the dominant minerals.

Oceanic crust is the crust beneath the ocean.  oceanic crust is 5 to 10 km thick. Oceanic crust is mostly composed of dense basalt rocks.


 the mantle is the layer between crust and core. The mantle is about 2900 km thick. The mantle starts at around 40 km beneath the surface of the earth. the mantle is mostly composed of semi-liquid ultramafic rocks. Most of the information about mantle is known from seismic studies. In the mantle, temperature and pressure increase with depth. the mantle is divided into two layers: upper mantle and lower mantle.


The core is the innermost layer of the earth. The core starts around 2890 km beneath the surface of the earth. The core is about 3500 km thick and composed of iron and nickel. The core has two distinct layers outer core and inner core.

The outer core consists of molten iron and nickel due to high temperatures. The inner core is solid due to high pressure.

The physical layers of the earth

The physical properties of the Earth vary with depth. These physical properties are associated with changes in temperature, pressure, and density. According to physical properties, the earth is divided into five layers: lithosphere, asthenosphere, mesosphere, outer core, and inner core.

1. lithosphere

 The lithosphere is the outermost physical layers of the earth. Earth’s crust and uppermost mantle together constitute the lithosphere. The lithosphere is the cool, rigid, and brittle and around 100 km thick layers of the earth. Lithosphere lies above the asthenosphere. The part of the mantle that constitutes the lithosphere has similar chemical properties to the mantle, but it’s solid like the crust. The lithosphere is fragmented into moving plates that contain the world’s oceans and continents.

2. Asthenosphere

  The asthenosphere is a weak layer of the rocks that easily deform. it’s extended from 80 to 200 km. Asthenosphere lies below the lithosphere and within the mantle. The asthenosphere is composed of hot and semi-liquid materials.  Some geologists believe that lithosphere floats on the asthenosphere.

3. mesosphere

 The mesosphere extended between the asthenosphere and outer core. The mesosphere is a region with high temperature and high rock strength. Rock in the mesosphere flows more slowly than rock in the asthenosphere.

4. outer core

           The outer core is lies between the mesosphere and inner core. It is a hot liquid layer where molten nickel and iron exist. It is conductive layers and responsible for the earth’s magnetic field.

5. Inner core

        it is the innermost layer of the earth.  inner core mostly composed of solid iron and nickel.  The reason for this layer to be solid is extremely high pressure.

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