Ice Ages

Ice Ages

1. What is an Ice Age?

   • Glacial period
   • Last one during the Pleistocene Epoch

2. Possible causes of Ice Ages

   • CO2 decrease
     • Decreased greenhouse effect
   • Continental drift
     • Ice forms on land near poles
     • Snow occurs at high latitudes
     • Snow occurs at high altitudes
     • Ice sheets increase albedo
   • Milankovitch Cycles
     • Changes to the Earth's orbit and eccentricity
     • Wobble in the tilt of the Earth
   • Variation in cosmic radiation
     • Magnetic reversal removes magnetic field
       • Cosmic flux increases and causes ice age

3. Ice cores

   • Lake Vostok
     • One of the largest subglacial lakes in the world
     • Site of ice core collection
   • What can ice cores show?
     • Abundance ratios of O18 in the past
       • O18 condenses before it reaches the poles during an ice ages
     • Changes in C02
       • Bubbles trapped in the ice analysed by gas chromatography
     • Changes in methane
     • Changes in temperature
       • Ratio of 018 and 016 measured
         • The colder it is, the less O18 will be at the poles
     • Benthic forams
       • Floor dwelling fossils containing isotope ratios