Erosion

Erosion is the wearing away of the rocks because of the action of external geological agents. The erosion gets implicit the transport of the erode materials, unlike the weathering.

 · Here we have some factors that take part on the erosion:

- Slope (with more slope, the erosion will be more marked because the materials are going to have a bigger speed, and that produces more slope).

- Weight of materials (is not the same just water, than water mixed with sand, the weight is different and the erosion that it produces it's different).

- Lack of cohesion (the cohesion will be less when there are cracks, when the rock is very weathered, etc).

- No vegetation ( when there's no vegetation, the erosion is so much serious).

- The climatic factor (depending on the weather, we will have a different erosion. It's not the same the erosion of the rain than the erosion of the snow).


· Erosion types on mountainsides: 

- Landslide (desprendimiento): abrupt fall of loose rocks downwards or the drop of the ground because of the gravity action.

Landslide

- Avalanche: big detachment of loose rocks. Powerful avalanches have the capability of transporting trees, ice, rocks, etc.

- Landslide (deslizamiento): it is produced when the ground slips or slides with other one. Between that two grounds there's a take-off surface.

- Flux: mud rivers which are produced when it falls down abruptly because of his plasticity.

· Erosion phenomena: 

- Creep: when a ground get wet, his volume increases and when this happens, the particle moves straight. Then, when the ground gets dry, the particle doesn't come to his original place, unless that by the gravity effect, it goes down.

Creep

- Gully: they are channels which are formed by the water's action. They're formed at the soft rocks' mountainside, so that's why they're sinking a little, because of the low hardness of the materials. When we've formed a gully, we can haver to consequences at the relief: fairy chimney and land piramides.

Fairy chimneys