1. Erosion and Weathering: Mountains are constantly being eroded by wind, rain, ice, and gravity. This breaks down the rock into smaller pieces called sediment.
2. Transportation: The eroded sediment is then transported downhill by wind, water, and gravity. Rivers carry sediment downstream, glaciers grind and carry rock debris, and wind blows sand and dust across vast distances.
3. Deposition: As the transporting forces lose energy, they deposit the sediment. This happens in low-lying areas like valleys, river deltas, and coastlines.
4. Compaction and Cementation: Over millions of years, layers of deposited sediment accumulate. The weight of the overlying sediment compacts the lower layers. Groundwater carrying dissolved minerals can then cement the sediment particles together, turning them into solid rock.
5. Gradual Leveling: As these processes continue, the deposited sediment gradually fills in valleys and lowlands, creating vast plains.
In the case of a worn-down mountain:
* The mountain's peak would have been eroded, leaving behind a lower, more rounded form.
* The eroded material would have been transported away from the mountain.
* This material would contribute to the formation of plains in lower areas, not directly on the mountain's original summit.
Therefore, plains don't form directly from the top of a worn-down mountain. They form from the sediment eroded from mountains and other sources, which is transported and deposited elsewhere.
