What is the term for the solid rock that underlies all parts of the land surface?

The term for the solid rock that underlies all parts of the land surface is bedrock. Bedrock refers to the solid, unweathered rock that lies beneath the loose material of the Earth's surface, such as soil and regolith. This foundational rock can be composed of various types of rock, including igneous, metamorphic, or sedimentary.

In contrast, regolith is a layer of loose, fragmented material that covers the bedrock and includes soil, weathered rock, and other organic matter. Soil is specifically the upper layer of regolith that supports plant life, consisting of organic matter, clay, silt, and sand. The Earth’s crust is the outermost layer of the Earth, which includes both the bedrock and the loose materials above it, making it a broader term that does not specifically refer to the solid rock alone. Therefore, bedrock is the most precise term to describe the underlying solid rock beneath the surface materials.