Question

what is "ice age"?

Answer 1

Ice ages are periods when the earth is much colder than usual. They are long enough and cold enough for glaciers to extend to the middle latitudes. The movement and the melting of thes glaciers causes great changes in the geology.

The last ice age started about 30,000 years ago, and lasted about 10,000 years. For more about it, see
http://www.esd.ornl.gov/projects/qen/nerc130k.html