树木有年轮,科学家发现南极大陆的冰也有年轮。原来,南极大陆的冰是由降雪积成的。南极冬季气温低于-80℃, 夏季也在-50℃,因此,雪永远不会融化,积雪一年比一年厚。夏季, 受太阳的直射,雪的结晶比冬季的排得紧密。这样,一年中下的雪,一层比较紧密,一层比较稀疏,其中就留下了一条明显的分界线,这就是南极冰的年轮。 The tree has annual rings, and scientists found that ice in the Antarctic continent also has annual rings. It turned out that the Antarctic ice is accumulated by the snow. Antarctic winter temperatures below -80 ℃, summer is also -50 ℃, therefore, the snow will never melt, snow year after year thicker. In summer, by the direct sunlight, the crystallization of snow is more intense than in winter. In this way, snow in a year, a relatively dense layer, a layer of relatively sparse, which left a clear dividing line, which is the Antarctic ice ring.