雪块从山崖上崩塌下来,这就叫做雪崩。在冬季,高山上的雪特别多,有的山由于很高,山顶的积雪甚至到夏季也不完全消融,形成了山顶万年白头的情况。高山积雪,便是雪崩产生的主要原因。高山上的雪愈积愈厚,有些地方的雪,受到上面新雪不断复盖的压力,便变得密实起来。最初成为“雪冰”(就是一种糊状冰),以后又成为冰块。如果能看到厚积雪层的剖面,那么,它的层次是十分清楚的,表面上是疏松的新雪,下面是雪冰层,再下面是冰层。愈下面,积雪的 The snow blocks collapsed from the cliff. This is called an avalanche. In the winter, the snow on the mountains is particularly high, and some mountains are very high. The snow on the top of the mountain does not completely melt into the summer, and it forms a long white head on the top of the mountain. Alpine snow is the main reason for the avalanche. The snow on the mountains is getting thicker and thicker. In some places, the snow has become dense because of the pressure of continuous snow cover. It became “snow ice” (it is a kind of paste ice) at first and later became ice cubes. If you can see the profile of a thick layer of snow, then its level is very clear, the surface is loose new snow, below the snow and ice layer, followed by ice. The more below, the snow