Fold Mountains form the world’s most extensive ranges, including the Alps, Andes, Appalachians, Himalayas and Rockies. Plates pushing against each other formed all of these ranges.
For example, the Himalayas are a fairly recent fold mountain range. Their history begins about 180 million years ago. This is when the ancient super-continent of Pangaea began to break up. At that time, the land that forms the present-day India lay a long way from Asia. It was sandwich between southeastern Africa and Antarctica and a huge ocean, called the Tethys Sea, that laid between it and Asia. As Pangaea broke up, the Indian plate began to move away from Africa and Antarctica and to drift slowly towards Asia.
Around 50 million years ago, the Indian plate was starting to push against the Asian one. As it moved forwards, the level rock strata and sediments on the bed of the Tethys Sea were squeezed together and folded upwards into large loops. In time the Tethys Sea vanished and the folded rocks formed the Himalayas which now join the Indian and Asian plates.
The enormous pressure between the plates greatly compressed the rock in the Himalayas. The folding explains why fossils of sea creatures are often found near the tops of the largest mountains.