Many know about the layers present above the Earth’s surface but do they know about the layers present below the Earth’s surface or the atmosphere? Like the space above us is divided into layers, the Earth below us is also divided into layers with the core being the innermost layer.
These layers are the lithosphere, asthenosphere, mantle, outer core and inner core. Two layers that are often found difficult to differentiate are the lithosphere and asthenosphere. But it is important to learn to differentiate between the two.
Lithosphere vs Asthenosphere
The main difference between Lithosphere and Asthenosphere is that the varieties of elements found on the lithosphere are larger than that in the asthenosphere. The lithosphere consists of 80 elements and 200 mineral types whereas asthenosphere mainly contains iron-magnesium silicate.
The lithosphere is the layer present below the atmosphere and it consists of the Earth’s crust along with the uppermost solid layer of the mantel. This is the layer where the tectonic plates lie that are the cause of earthquakes, tsunamis and volcanic eruptions.
The asthenosphere is the layer below the lithosphere. It is made of the uppermost weaker layers of the mantel and has a depth of 700 km from the Earth’s surface. They are rather semi-fluid and allows the movement of their half molten rocks.
Comparison Table Between Lithosphere and Asthenosphere
| Parameters of Comparison | Lithosphere | Asthenosphere |
| Position | Below the earth’s surface and atmosphere | Below the lithosphere |
| Depth | 80km to 200km below the earth’s surface | Extends to 700 km below the earth’s surface. |
| Components | Crust and uppermost solid mantel | Consists of the uppermost weaker part of the mantel |
| Physical structure | Rigid, brittle and elastic that contains the tectonic plates | Mostly solid with some partially molten rocks that exhibit the characteristics of plastic. |
| Characteristics | Elastic and ductile | Is more ductile than the lithosphere |
| Mineral contents | Of nearly 80 element and 2000 minerals. | Mainly contains iron-magnesium silicate. |
| Temperature | 400 degree Celsius approximately | Can vary from 300 to 600 degree Celsius. |
What is Lithosphere?
The lithosphere is the uppermost layer of the Earth. It lies right below the atmosphere and has a varying depth of 80 km to 200 km below the Earth’s surface. The lithosphere is divided into two parts: crust and the uppermost solid mantel layer.
Since the lithosphere includes the crust, it is the place for different varieties of elements and mineral compounds. Statistically, the lithosphere has 80 varieties of elements along with 2000 other mineral compounds.
The concept of lithosphere was developed in 1911 by Barrell. This was because there was a gravitational field present that led to his belief of having a strong upper layer of Earth.
At the lithosphere-asthenosphere boundary, the molten rocks condense to form brittle rocks that break down. These are called tectonic plates whose movement causes earthquakes and other natural disasters.
What is Asthenosphere?
The asthenosphere is the layer present below the lithosphere. They consist of the uppermost weaker layer of the mantel and has a depth of 700 km from the Earth’s surface.
The asthenosphere is mostly solid except for a few regions that have half molten rocks and are thus semi-fluid. This is the reason of their ductility and their characteristic features resembling that on plastic.
The concept of the asthenosphere came in 1926.
Since the rocks are half molten and the layer is semi-fluid, it allows movement of these rocks. This is the cause of the movement of the tectonic plates in the lithosphere. Therefore, the movement of the half molten rocks in the asthenosphere is what causes natural disasters.
Main Differences Between Lithosphere and Asthenosphere
- The lithosphere is located right below the Earth’s atmosphere whereas the asthenosphere is located right below the lithosphere or the uppermost solid mantel layer.
- Lithosphere has a depth of about 80 km to 200 km below the Earth’s surface. In the case of the asthenosphere, it has a depth of 700 km below the earth’s surface.
- The lithosphere consists of the earth’s crust and the uppermost solid layer of the mantel. But asthenosphere consists of only the uppermost weakest layer of the mantel.
- The physical structure or characteristic of lithosphere can be described as rigid, brittle and elastic. This is the layer that consists of the tectonic plates. The characteristics of the asthenosphere, on the other hand, is described as mostly solid with partially molten rocks that give it a semi-fluid texture.
- The lithosphere is elastic due to the crust and the tectonic plates being a part of this layer. It is ductile as well. But asthenosphere is more ductile than lithosphere because of the molten rocks and their fluid movements.
- Since the lithosphere consists of the Earth’s crust that has the highest source of mineral content a variety of 80 elements and 2000 minerals can be found. But the asthenosphere mainly contains only iron-magnesium silicate since it is molten rocks or lava.
- Since the asthenosphere consists of the molten rocks and is closer to the Earth’s core, it has a varying temperature of 300-600 degree Celsius. But the lithosphere has an approximate temperature of 400 degree Celsius.
Conclusion
Like the space above Earth, the land below the Earth’s surface are also divided into different layers. The top two layers being lithosphere and asthenosphere. These are the layers that are often difficult to differentiate as they both have a part of the mantel.
The lithosphere is the layer below the atmosphere that consists of Earth’s crust and the uppermost solid layer of the mantel. They have a depth of 80km to 200km and have various mineral contents present.
The asthenosphere is the layer below the lithosphere that consists of the uppermost weaker layer of the mantel. They are solid except for the half molten rocks that give it a semi-fluid flow and can follow all the properties of plastic.
While the lithosphere is mostly solid and contains the tectonic plates that cause many natural disasters, asthenosphere contains mainly the half molten rocks that give it a fluid flow. This fluid flow of the components of the asthenosphere is the reason for the movement of the tectonic plates.
Reference
- https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2012GC004060
- https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/JB081i020p03525