Moving tectonic plates are responsible for some of the Earth’s major landscape features. If a large slab of the Earth’s surface is gradually squeezed, the solid rock slowly wrinkles and crumples. Layers of rock become wavy folds. If the rocks are stretched or squashed together quickly, they crack or split apart. These cracks are known as faults.

Mountain building

When two tectonic plates push together, the rocks slowly crumple and fold up. This is how mountain chains are created. It happens over millions of years—far too slowly for us to notice.

The world’s great mountains, including the Himalayas in Asia, Andes in South America, Rockies in North America and Alps in Europe, are all fold mountains. The Himalayas are actually getting higher, as two tectonic plates continue to push against one another.

The tops of some mountains are so high that they are covered in snow and ice all year round. There is less oxygen in the air to breathe.

As the mountains "grow”, they are attacked by wind, rain, frost and ice. The rocks break up, leaving behind sharp edges. These forces of weathering and erosion produce jagged peaks. Eventually, after many millions of years, the peaks will be worn down to become low, rounded hills. The Appalachians in eastern North America are an example of an "old" mountain range like this.

Rift valleys

Faults are cracks in the Earth’s crust. They form where the rocks break under pressure from moving tectonic plates. A block of land sometimes slips down between two faults to make a valley. This is called a rift valley.