The term 'Layer of Earth' can be broken down into two crossword solutions: MANTLE (6 letters) and SOIL (4 letters). The MANTLE is the layer of Earth located between the crust and the core. It is composed of hot, dense rock and is about 2, 900 kilometers thick. SOIL is the top layer of the Earth's surface and is composed of organic matter, minerals, and other materials. It is important for supporting plant life and is essential for agriculture.