1. Rivers deposited huge quantities of sediments in depressions called geosynclines.
2. Over millions of years the sediments were compressed into sedimentary rocks such as sandstone and limestone.
3. The plates move together (a compressional boundary) forcing the sedimentary rock upwards into a series of folds.
Deposition - when material is dropped from a load of material.
Geosyncline - a large depression between two plates.
Compressional plate boundary - where an oceanic and continental plate converge into eachother.
Andes - South America
Alps - Europe