Fold Mountains Mountains formed when two Plates Collide.
Fold Mountains • Fold mountains are mountains that are made when two of the earth’s plates collide. • When two plates collide the pressure compresses the rocks, forcing them to buckle and fold. Think of what happens to the bonnet of a car during a crash.
Evidence of Folding • Scientists have found fossils of dead sea creatures thousands of metres up in the Andes in South America. • These creatures lived in the sea, and their remains sank to the ocean floor when they died. • Their remains were trapped in newly forming rocks which are later pushed up from under the sea when plates collide to make fold mountains.
Ridge and Valley Landscape • When the two plates collide the crust buckles and folds. This creates a pattern of ridges and valleys. • The downward part (the valley) is called a syncline. • The upward part (the ridge) is called an anticline.
Young Fold Mountains • As we know from previous sections, the earth’s plates are constantly colliding in different parts of the world. These collisions are still increasing the height of some fold mountains today. • The world’s young fold mountains are already about 30-35 million years old. • These mountains are called Alpine Fold Mountains. They are very high because they have not been worn down by weathering and erosion.
Alpine Fold Mountains • There are 4 major mountain ranges formed during the Alpine Folding period. These are, • 1. The Rockies in North America. • 2. The Andes in South America. • 3. The Alps in Europe. • 4. The Himalayas in Asia.
Armorican Fold Mountains • Ireland’s fold mountains were formed hundreds of millions of years ago. • They were formed in Munster about 250 million years ago, and were once as high as the Alps. • However, weathering and erosion have worn them down over millions of years and they are now much smaller. • Examples include the Magillicuddy’s Reeks, The Galtees, The Comeraghs, and The Knockmealdowns.