Why the debris flow?

Why the debris flow?
Debris flow is a natural disaster.
When the debris flow occurs, the flood not only a large number of sand and stones, but also mixed with floods or snow melt water, etc., they are mixed into a thick mud, like runaway wild horses in general along the steep slope down.
Debris flow to the place, farmland become desert, houses become ruins, destroyed the embankment, bridges, human life and property to bring great losses.
According to statistics, the world every year nearly 100,000 times the large and small debris flow.
In 1970 the Peruvian Andes in South America had a glacier debris flow, more than 3010 million cubic meters of snow and mud and mud suddenly into a town called Luo Jiayi, instant, the city was completely buried, 30,000 residents were killed
.
Debris flow is caused by loosening of the mountain, often occurs in semi – arid mountainous areas or plateau glacier area… …
Here steep terrain, little vegetation, once the rainstorms or glaciers thaw, stones absorb enough water, they appear loose, began to move down the slope.
With each other extrusion, collision, large and small debris mixed with mud water, merged into a huge torrent rolling down, so there has been debris flow.