Many of the world's highest mountain ranges are fold mountains. They began to form millions of years ago when plates pushed together. The Himalayas and Alps are chains of fold mountains. Some mountains, such as Mount Everest, are still growing in this way.

If pressure builds up under the Earth's surface, brittle rocks in the crust may crack. Cracks in rocks are called faults. If two faults occur close together, the chunk of crust between them may be pushed up or slip down below the surrounding rock. Chunks that are pushed up are called block mountains or horsts. A low area between two horsts is called a rift valley.

The most famous rift valley is the Rift Valley in East Africa. The Rhine Valley in Germany and Death Valley in the USA are also rift valleys.

In some areas, currents of magma under the crust flow together from opposite directions. The pressure may squeeze the crust and make it buckle and form folds such as those shown here:

The Alps are a young fold mountain belt (30-40 million years old) spread over parts of: France, Italy and Switzerland. The area was covered in glaciers during the last ice age and they have left behind features such as pyramid-shaped mountain peaks, U-shaped valleys and long, ribbon lakes. As altitude (height) increases, the climate becomes colder and this affects land use:

• Farming is traditionally carried out on the valley floors where the soils are deeper and more fertile. On the sunnier south-facing sides, fruit can be grown. In the winter, farmers keep their animals on the valley floor until the snow melt in the spring means they can be moved back onto higher pastures.

• With its central location in Europe, tourism is now a major industry. There are many places in the Alps which tourists are attracted to visit, such as Chamonix and St Moritz. Sports such as skiing and sledging are popular in the winter, whilst hiking and climbing are popular in the summer when there isn't any snow. The money brought into Alps have helped improve transport links, with many new roads, railway lines and cable cars being built. At 16.4km (10.2 miles) long, the St. Gotthard Tunnel is the third-longest road tunnel in the world.

• Many of the Alpine slopes up to 1,800m are covered with coniferous trees. Their wood is used for: fuel, building material and paper making. In Switzerland, the wood is also used to make cuckoo clocks.

• The fast-flowing rivers fed by snowmelt and high mountain gorges which are easy to dam make the Alps a great place to generate hydro-electric power which can be used by local industries.

The Alps are a challenging place to live however because:

• the steep mountain slopes make it difficult to build houses and roads on;
• there is little flat land to farm on;
• heavy snowfall can make travelling difficult during the winter;
• areas can be at risk from sudden snowfalls from mountain sides called avalanches.