The formation and development of avalanches can be divided
into three sections, namely, formation zone, passage zone
and accumulation zone.
An avalanche mostly forms in the upper part of the mountain,
where the snow is rich and thick. For example, the high snow waves,
gradient that exceed 50 to 60 degrees, the lower end of the glacier,
etc, are the formation areas of avalanches.
Passage zone of avalanche is under the formation zone, which is
often a straight u-shaped groove from top to bottom. Because avalanches
often pass through, despite being covered with snow, the groove
is still very smooth, without big ups and downs or obstacles and
its length can reach up to several hundred meters and width, 20 ~ 30
meters but it is not too wide, or the snows that slide down
are not very concentrated, which cannot form an avalanche.
Accumulation zone is immediately below the passage zone,
which is the place that snow slide body stops due to the moderate
slope foot. Looking from the morphology, it seems like a pyramid.
So it is also called avalanche cone or avalanche heap.