Tectonic fault/zone of weakness

Tectonic faults are weak points in the rock formations of the Earth’s crust. They are caused by slow flow movements deep within the Earth which change the positions of the various crustal plates (see image). There are three main forms of tectonic fault:


Convergence boundaries (subduction zone)

Two plates collide and one dips below the other. The consequences are explosive volcanism and frequent earthquakes. Examples of typical convergence boundaries are the Andes and the Mariana trench in the Pacific.


Divergence boundaries

Two plates move away from one another. In these zones of expansion, new crust is «welded» to the plates and shield volcanoes are formed. Examples of regions typical of this phenomenon are the central mid-ocean ridge, the Rhine rift valley and the East African rift valley.


Transform boundaries

Two plates drift past each other laterally, often accompanied by earthquakes. The San Andreas Fault in California and the North Anatolian fault are typical examples of transform faults.