In geological terms, it does not take long to see significant changes in ice cover on Earth. Eighteen thousand years ago was the peak of the last ice age. Now, in the modern era, we are in a warm period between glacial advances.

 

 

Ice sheets used to stretch down and cover most of Canada and some of the United States (left image). In Europe, northern Germany and Poland were covered by ice.

 

 

18,000 years ago (recent in geologic terms) Antarctica was covered by ice sheets up to four kilometers thick!