Glaciologists believe that there have been five major Ice Ages (when large areas of the Earth’s surface were covered with ice). Each Ice Age was followed by a period when the earth seemed to be ice free even at higher latitudes. The five ice ages are named: the Huronian, Cryogenian, Andean-Saharan, Karoo Ice Age and Quaternary Ice Age.

The Huronian formed around 2.4 to 2.1 billion years ago. The Quaternary Ice Age is our current ice age and started about 2.58 million years ago.

Inside each Ice Age there were cycles of glaciation with ice sheets advancing and retreating on a 40,000-year timescale. They are called “glacial” when they advance and “inter-glacial” when they retreat. The Earth is currently in an inter-glacial period. The glacial period ended about 10,000 years ago.

Studying the first four ice ages is difficult as each subsequent glacier obliterates the previous. Accordingly, the most studied Ice Age is the current, Quaternary.