It made the ice thin. If he stepped there, he might break through the ice into a pool of water.

VOA: special.2010.05.01

And it's dangerous. People slip and fall on the snow because it's made of ice.

这样也很危险，人们会在雪上滑倒，因为雪里面都是冰。

I'm glad 实战 - SpeakingMax英语口语达人