1. Formation of Rifts and Grabens:
* Rifts: These are areas where the Earth's crust is being pulled apart. As the crust thins, it often breaks along faults, creating a depression known as a graben.
* Grabens: These are down-dropped blocks of land bounded by faults. They are common features in rift zones and often form valleys or depressions.
2. Volcanic Activity:
* Extension can cause magma to rise from the mantle, leading to volcanic activity. This is particularly common in mid-ocean ridges and continental rift zones.
3. Earthquakes:
* As the crust stretches and breaks, earthquakes can occur along the faults. These earthquakes are often shallow and have a characteristic "normal faulting" mechanism.
4. Formation of New Crust:
* In areas of intense extension, particularly at mid-ocean ridges, new oceanic crust is created. This process is called seafloor spreading.
5. Formation of Fault-Block Mountains:
* In some cases, the blocks of crust that are pulled apart can be uplifted, creating fault-block mountains. These mountains have steep slopes on one side and gentle slopes on the other.
Example: The East African Rift Valley is a classic example of a continental rift zone where the Earth's crust is being pulled apart. This process is responsible for the formation of numerous volcanoes, grabens, and the Great Rift Valley itself.
In summary: When rocks are pulled apart by tectonic forces, it results in extension, leading to the formation of rifts, grabens, volcanic activity, earthquakes, and even the creation of new crust.
