• Ice Age – Period of
millions of years where
continents were
repeatedly glaciated
• Glacial period – time within an ice age where glaciers advanced
(grew) more then they retreated (shrank)
• Interglacial period – time within an ice age where glaciers retreated
more than they advanced
When did they occur?
As recently as 15,000 years ago, much of N. America was covered in ice
during the last ice age.
What are some possible reasons for ice
ages?
• Plate Tectonics
• Reduction of CO2 in the atmosphere
• Volcanoes
• Milankovitch Theory
Milankovitch Theory
• Ice ages occur in cycles
• Milutin Milankovitch (Serbian scientist) proposed
that this regular cycle was the result of three
things
Orbit
Wobble
How do Scientists
Know When Ice Ages
Occurred???
- Fossils