Most of the dry land on Earth sits no more than a few hundred metres above sea level. But in some places mountain belts rise to heights of several kilometres.These regions are often prone to devastating earth tremors. How are mountains formed and what is the connection with earthquakes? The answer may lie in the fluid-like properties of the Earth's outer layers. According to a new theory, mountains may flow up or down when continents collide. In the process they affect the circulation of the planet's atmosphere and change the climate.

• Aubrey Manning