New mountains are formed as rocks are forced higher by the movement of the Earth's crust's enormous rocky plates. The rocks are forced higher in two ways: fold mountains develop when layers of rock collapse, and block mountains form when massive masses of rock rise or fall. These changes occur over very long periods of time (geologists say millions of years) but they can also happen rapidly due to earthquakes or volcanic activity.
Mountain building occurs all over the world but the most significant deposits are in the Himalaya and Andes mountains. There are several types of mountains including volcanoes, mesas, spires and ridges. Volcanoes are the most dramatic example of mountain building and there are seven major volcanic regions on Earth. They include the Pacific Ring of Fire, which surrounds all of North America; the African Rift Valley; the Indian Ocean; the Argentine Piedmont; the Chilean Coast Range; and the Indonesian Archipelago.
Mountain ranges serve a number of important functions for humans. They provide water through precipitation and meltwater from ice caps and glaciers, and they affect climate by preventing heat from reaching the surface of the planet or blocking ocean currents. They may also contain valuable resources such as gold, silver, zinc, copper, coal, oil, and natural gas. Mountaintops are considered prime real estate today because they have access to sunlight for much of the year which is why forests grow up there.
When two or more of the Earth's tectonic plates collide, fold mountains form. Rocks and debris are distorted and folded into rocky outcrops, hills, mountains, and whole mountain ranges at these colliding, compressing borders. Fold mountains form as a result of a process known as orogeny. The term refers to the fact that these mountains are often folded.
Fold mountains can be very large. The Himalaya range in Asia is one such fold mountain system. It is made up of several peaks over 8,000 meters (26,247 feet) high, including Mount Everest (8,848 m/29,029 ft).
Fold mountains can also be small. A few hundred miles west of India is the island nation of Sri Lanka. It has many beautiful beaches, mountains, and jungles but also includes several small mountainous islands where life depends on fishing and tourism. One of these islands is called Kodachadri. It has only three hundred people living there but also has a peak called Madhu Pahar that reaches about 1,186 meters (3,937 feet).
The word "mountain" comes from Latin Mons, which means "hill." So, a fold mountain is simply a hill that has been folded together with other similar folds to create a larger hill or mountain.
When two plates collide, fold mountains occur (a compressional plate margin). This can occur when two continental plates or a continental and an oceanic plate migrate towards one other. The movement of the two plates pushes sedimentary rocks higher, creating a sequence of folds. In some cases, volcanic eruptions also contribute to fold formation.
Fold mountains are common in certain regions of Europe and North America where there is convergence between two plates. These include the Alps, Pyrenees, Ural Mountains, and Andes. They also occur near islands that were once part of a continent but are now separated by water, such as Hawaii and New Zealand.
Fold mountains can be very large, like in the case of the Himalaya range in Asia or the Rocky Mountains in North America. But they can also be quite small, like in the Painted Rocks area near Bend, Oregon. Here, the contact between two plates of rock has been folded along with any sedimentary layers within it, producing a series of small hills known as "painted rocks".
Fold mountains are important because they can contain oil or natural gas. There are many fields for oil production located within them.
In addition, they can provide evidence of past ice ages. The glaciers that move over fold mountains can cause them to rise up and then collapse, resulting in a pattern of flat surfaces interrupted by steep cliffs.