What fundamental concept explains the Earth's surface processes?

Plate tectonics is the fundamental concept that explains the Earth's surface processes. This theory describes the large-scale movement of the Earth's lithosphere, which is divided into several tectonic plates that float on the semi-fluid asthenosphere beneath them. The interactions between these plates are responsible for many geological events and features, including earthquakes, volcanic activity, mountain formation, and the creation of ocean basins.

The movement of tectonic plates can lead to various surface processes, such as the recycling of the Earth's crust and the formation of distinct landforms through processes like subduction, rifting, and collision. These interactions not only shape the landscape but also influence climate patterns and the distribution of ecosystems over geological time.

In contrast, the other concepts mentioned—biogeochemical cycles, thermodynamics, and astrophysics—play essential roles in understanding different aspects of Earth science, but they do not specifically address the dynamic processes that shape the Earth's surface like plate tectonics does. Biogeochemical cycles focus on the movement of elements and compounds through the Earth's systems, thermodynamics concerns the laws governing energy and heat transfer, and astrophysics deals with celestial bodies and the universe rather than geological processes on Earth.