Mud slides or avalanches appear due to gravitational currents of granule material in mountainous areas.
Landslides, rock-slides and mudslides or mud flows, occur due to a piece of land earth, rock, mud or a tree detaching from its surrounding land, and sliding downwards along the mountain slope, along the way dragging and tearing down and accumulating material, finally developing into a huge stream that can bury whole settlements.
They can be released by earthquakes, volcanic eruptions or a general instability of the soil. Vibrations, even thunder, excess weight from snow, the erosion of rivers, snow-melt or heavy rainfalls, can all cause loose soil on steep terrain to slide downwards. This can also happen because of by man made reasons such as, deforestation, the removal of deep-rooted vegetation, by stressing loose ground with too much weight of buildings or vibrations from traffic and machinery.
An avalanche is released on a mountain slope when the load of the upper snow layers exceeds the bonding forces of a mass of snow, bonding to the layer of snow beneath, adding to horizontal internal stability, and losing support from anchors such as rocks or trees. An avalanche can be incited by a sudden rise of temperature, by wind creating accumulations of snow, or sudden heavy snow fall, that creates an enormous weight that doesn’t have time to bond, or even by a vibration caused by sound like shouting or gun shots, or by a small amount of extra weight, like a skiing person.