The accumulated feature that moves at a very slow rate yet is able to carve new geologic features like mountains and valleys is erosion.

Here's why:

* Slow and Steady: Erosion is a gradual process, often happening over millions of years. It's the wearing away and transportation of rock and soil by natural forces like wind, water, ice, and gravity.

* Carving Landforms: While seemingly insignificant at first, the constant action of these forces slowly chips away at mountains, carves valleys, and shapes the landscape.

* Examples:

* Rivers: Over time, rivers can carve canyons and gorges.

* Glaciers: Glaciers can erode mountains, creating U-shaped valleys and leaving behind moraines.

* Wind: Wind can create sand dunes, sculpt rock formations, and carry away soil, leading to desertification.

While tectonic plates moving and volcanic activity are responsible for creating mountains and valleys in the first place, erosion plays a crucial role in shaping and re-shaping those features over time.