Many years ago, most of our earth was covered with blocks (块) of ice. These ice blocks were as tall as high buildings in modern cities. Most of the ice was in the northern part of the world. Then the ice blocks started to move south. Cold and rain came with the ice. Animals had to move. At last, the ice began to melt (融化). After half a million years, most of it melted. More than half of the earth became covered with water. Theclimatebecame much warmer. Things began to grow. The earth began to look the way in which it looks today.