Theymoved in with a local family, the Harrisons, and, like them, had littleprivacy, rare baths, and a blanket of snow on their quilt when they woke up inthe morning. Some mornings, Rosamond and Dorothy would arrive at theschoolhouse to find the children weeping from the cold. In spring, the snow was replaced by mud over ice.
这是2022高考考试英语全国卷一阅读理解B中的一个段落。请问其中的 mud over ice 是一种什么状况？冰上的泥土？冰上面如何会有泥土呢？泥土不是应该在冰的下面吗？
In spring, the snow was replaced by mud over ice.
参考译文：在春季，积雪被覆盖在冰面上的泥所取代。
备注：over为介词“覆盖在…上面” mud over ice=mud which is covered by ice
She put a blanket over the sleeping child.她给熟睡的孩子盖上毯子。
He wore an overcoat over his suit.他在西装外面再加了一件大衣。
She put her hand over her mouth to sTOP herself from screaming.她用手捂住嘴，以免叫出声来。
