Final answer:
Rocks appear stable and unchanging because weathering and erosion processes happen over geologic time, which extends far beyond the human timescale. Principles like uniformitarianism explain that the same geologic processes operating now have been at work for millions of years, making changes too gradual for humans to notice.
Step-by-step explanation:
Earth processes such as weathering and erosion are indeed constantly occurring, but the reason why rocks appear stable and unchanging to humans is that these processes often take place over very long periods of geologic time. Geologic time is enormous compared to a human lifespan, meaning that the changes in rocks and landscapes that occur as a result of weathering, erosion, and tectonic forces are usually too gradual to be observed in a human's lifetime.
Early geologists like Charles Hutton and Charles Lyell contributed to our understanding that the Earth's features are the result of slow and consistent change. They introduced principles such as uniformitarianism, which posits that the same geologic processes we observe now have been at work for millions of years, just at a very slow and steady pace. This principle allows us to recognize that while rocks may appear unchanging over the course of a human life, they are indeed transforming constantly at a rate that can be observed geologically by examining the rock record.
The geological carbon cycle, river valleys, and the formation of sedimentary rocks are all examples of geologic processes that have shaped the Earth's surface over vast periods of time. However, due to the long time scales involved, these transformations can often be imperceptible to casual human observation.