Figure 12.21: Just before the Phanerozoic, many parts of Earth were covered with glaciers.
After the Earth began to warm and many of the glaciers melted, there was an explosion of
new life on Earth. The glaciers in this picture are from the present. However, glaciers are
much less common on Earth today than at other times in Earth’s history. ( 4 )
Figure 12.22: The Phanerozoic Eon was often characterized by times of warm tropical cli-
mates. The age of the dinosaurs was especially mild for most of the Earth. This allowed
plants and animals to spread over large areas of land. This picture shows plants in a modern
rainforest. Plants of the Phanerozoic may have looked similar. ( 16 )