Building Up and Breaking Down

Earth  has an irregular surface because every time it is changing
it is building or making change.
As the crust move the rocks of the crust can change.
The rocks can change position  being broken ,twisted  or squezed.
That is why  the earth make changes the form of the crust.
But always is an end .They are two kind of forces that work to balanced
the Earth crust:
Weathering  and Erosion.
That is why it forms layers in the earth because every time an mountain or
 something like that it has its end  it weather  and it  falls down forming a mass wasting and one
layer more of the earth. Forming one of the layers of the earth :
Topsoil, Subsoil , Bedrock.