State some ways that erosion can happen. state how humans and animals can contribute to erosion. give some examples of human activities that cause or speed up erosion.

Erosion is the eventual ware away of materials (dirt, rock). Erosion can be caused by water (flooding, rain), deforestation, and human causes. One of the common forms of human caused erosion is a result of deforestation. Deforestation is the removal of trees in an area to make room for civilization. The trees and especially roots support the dirt. Without the trees, the dirt is more prone to erosion by natural causes. 

I'm not sure what your asking buddy.. but i know that you can weld two peices of steel by pure force and pressure.