**Mantle: A Significant Portion of Earth's Interior**

The mantle is a substantial component of Earth's interior, accounting for a significant percentage of its total mass. It is situated between the crust and the core and is primarily composed of solid rock materials. Understanding the composition and properties of the mantle is crucial for comprehending the dynamics of the Earth's interior, plate tectonics, and various geological processes.

**The Proportion of Mantle in Earth's Composition**

The mantle constitutes approximately 84% of Earth's total volume. It extends from the base of the crust, which marks the Mohorovičić discontinuity, to the core-mantle boundary, located at a depth of approximately 2,900 kilometers (1,800 miles). This vast portion of the Earth's interior is divided into two main regions: the upper mantle and the lower mantle.

**The Upper Mantle: A Dynamic Zone**

The upper mantle, which extends from the base of the crust to a depth of about 660 kilometers (410 miles), is a highly dynamic zone. It consists of solid rock materials that are subjected to immense pressure and high temperatures. The upper mantle is further divided into two regions - the lithosphere and the asthenosphere.

1. The Lithosphere:
- The lithosphere is the rigid outermost layer of the Earth, encompassing the crust as well. It is composed of the uppermost part of the mantle and the crust, and it is broken into several rigid tectonic plates.
- The lithosphere is responsible for the movement of tectonic plates and plays a significant role in shaping the Earth's surface through various geological processes like earthquakes, volcanoes, and mountain formation.

2. The Asthenosphere:
- Situated below the lithosphere, the asthenosphere is a partially molten region in the upper mantle.
- The asthenosphere is characterized by its weak and ductile behavior, enabling it to undergo plastic deformation under high pressure and temperature conditions.
- Its ability to flow allows for the movement of tectonic plates over the rigid lithosphere, driving the process of plate tectonics.

**The Lower Mantle: A Solid and Robust Zone**

The lower mantle extends from a depth of about 660 kilometers (410 miles) to the core-mantle boundary. It is a solid and robust region, composed mainly of silicate minerals and iron-rich compounds. The lower mantle experiences extremely high pressures and temperatures, which significantly influence its properties and behavior.

**Conclusion**

In conclusion, the mantle constitutes approximately 84% of Earth's volume. It is a vital part of the Earth's interior, consisting of the upper and lower mantle. The upper mantle, including the lithosphere and asthenosphere, plays a crucial role in plate tectonics and geological processes, while the lower mantle is a solid and resilient region beneath it. Understanding the composition, behavior, and dynamics of the mantle is essential for comprehending various geological phenomena and gaining insights into Earth's evolution.