The theory explains the how and why behind mountains ... takes place at four types of boundaries: divergent boundaries, where new crust is formed; convergent boundaries, where crust is consumed ...

Build mountains ... For more on divergent boundary, go to The Sea Floor Spread. Also known as subduction boundary, a convergent boundary occurs where one plate slides under another as the two ...

These convergent boundaries also occur where a plate ... often spewed out in volcanic eruptions such as those that formed some of the mountains in the Andes of South America.