The name of the substance that makes up the outer layer of the Earth is called the lithosphere. This layer includes the crust and the upper mantle and is composed of solid rock, minerals, and soil. The lithosphere is divided into tectonic plates that float on the semi-fluid asthenosphere beneath them. These plates interact at their boundaries, causing geological phenomena such as earthquakes, volcanic activity, and the formation of mountains. Understanding the lithosphere plays a crucial role in geology, helping scientists study Earth's structure, natural resources, and the processes that shape the planet over time.