What is an ice age?
A period of time when large parts of the earths surface is covered in ice
Foraminifera -evidence
Forams form differently depending on temp of water
Oxygen isotopes - evidence
017- rare
018 heavy
016- lightest
When warm 016 returns and ratio stays the same
During cold 016 is locked in ice and doesn't return
Ice cores - evidence
Bubbles of air get trapped in ice. Can tell us oxygen isotope ration in atmosphere
most recent ice age
Pleistocene ice age
How do ice ages develop
Cold periods develop very gradually
Earth-Sun Relationship-cause
Earths elliptical path has changed
More narrow and wider through time
Changes distance to sun
solar activity-cause
Suns output has likely varied through time
Ocean currents-cause
If currents were slower or shut down, warm waters may not flow north or south
Continent movement - cause
Continents moving apart and together can have an affect on ocean currents, not flowing as well
Effects of an Ice age
Climate is variable - but still extreme
Low sea level
Amazing landscapes