rock being worn down and having the sediments carried away
land building: new land being formed, either by tectonic uplift or by lava flows or by the deposition of sedimentSource(s):Let's use the Rockies as an example. They are a young mountain range, tall and beautiful, but erode away constantly. The sediment is moved away by rivers which can fill and change direction forming new river channels. Some scientists think they could have been twice as tall in their early days. The Appalachians are very old and worn down. The sediment has filled many of the valleys nearby. These were once thought to be as majestic as the Rockies.
There is a couple good examples for you :)
