Existing mountains and land DO contribute to the upbuilding of a continent, but it's not the only process.
Here's how it works:
* Erosion: Weathering and erosion break down mountains and existing landmasses, producing sediment like sand, silt, and clay.
* Transportation: Rivers, wind, and glaciers transport this sediment to lower elevations, often ending up in oceans.
* Deposition: This sediment settles on the ocean floor, forming layers over time.
* Subduction and Accretion: Oceanic plates carrying these sediment layers can collide with continental plates. The denser oceanic plate is subducted, and the sediment layers are scraped off and added to the edge of the continent, building it outwards.
Therefore, existing mountains and land indirectly contribute to continental growth through erosion, transportation, and accretion.
However, other processes are also crucial for continental growth:
* Volcanism: Volcanoes, especially along subduction zones, can erupt and deposit large amounts of new material onto the continents.
* Plate Tectonics: The movement of tectonic plates can cause collisions that uplift landmasses, forming new mountains and expanding continents.
In summary, while existing mountains and land play a role in providing material for continental growth, it's just one part of a complex and dynamic process involving various geological forces.
