|Although rocks appear to be absolutely stable and to
remain in place forever, they are much more mobile than it at first appears.
They move thousands of kilometres on tectonic plates, collide with each
other and form mountains. Some mountains are still increasing in height,
while others are shrinking. Along tectonic plate margins, there is often
a high risk of earthquakes and volcanic activity. Besides, rocks have
their own life, called rock cycle. The cycle explains how rocks are formed,
but also how they are eroded and transported, e.g. by glaciers, wind or
rivers, from high elevations and re-deposited in the valley. In addition,
rocks represent an important foundation for the ecosystem, since they
deliver many nutrients for plants. So it is worth having a closer look
at rocks in this unit.