An ice age is a period when large expanses of ice sheets cover the land. millions of years ago, an ice age occurred on earth. fossils of animals buried under this ice were obtained. the organisms were frozen solid shortly after death, which made them: 1original-tissue fossils 2mineralized fossils 3trace fossils . a mass extinction occurred during this period, which means that: 1many species migrated from one place to another 2 many species were wiped out 3 many species emerged during the ice age .