Which layer of Earth constitutes the great bulk of its volume?

The mantle constitutes the great bulk of Earth's volume, making it the largest layer within the planet. This layer lies between the crust above and the core below, extending to a depth of about 2,900 kilometers (1,800 miles). The mantle accounts for approximately 84% of Earth's total volume, which is significant compared to the crust and core.

The mantle is composed primarily of silicate minerals and is characterized by its ability to flow slowly over geological time scales. This flow is crucial for processes such as plate tectonics and mantle convection, which contribute to various geological phenomena including earthquakes and volcanic activity.

In contrast, the crust is relatively thin and makes up only a small part of Earth’s overall volume. The core, while being the central part of the Earth and responsible for generating its magnetic field, also does not contribute as much to the overall volume as the mantle does. The asthenosphere, while an important part of the upper mantle that allows tectonic plates to move, is just a subdivision within the larger mantle layer, further emphasizing why the mantle is the correct answer.