1.   Began 2-3 mya  Last glacial period ended 15,000 years ago  Pleistocene epoch  Ice covered 30% of Earth’s land  Indirect effect of Ice Age glaciers:  Migration of animals and plants  Rebounding upward of crust  Worldwide change in sea level  Climatic changes 1 Ice Age Figure 6.22: Max extent of ice during the Ice Age. Glacier Power, (3:34) Formation of Glaciers, (3:50)

2.   Time of low temperatures  Time of glacier advances  Interglacial: warm periods within an ice age  Currently: Holocene epoch interglacial  Theory: current warm climate another 50,000 years  Glacial periods named by geographic distribution  Wisconsinian (26,000-13,000 ya) ice sheets to 45 N  Ice sheets 3-4 km thick  Isostatic rebound: reshapes land after ice removed Isostatic rebound:  Illinoian (300,000-100,00 ya)  Pre-Illinoian (2.5-0.5 mya) 2 Glacial Period Google Images, Gulkana glacier in Alaska

3.   Core sample removed from ice sheet  Contains ice formed over many years  Provide more info than tree rings, sediment layers  Ice properties, inclusions Ice  Used to reconstruct temperature records  Contain atmospheric composition  Contains wind blown dust, ash, gas bubbles  Contain radioactive substances  Records: temp, ocean volume, atm chemistry and gas composition, volcanic eruptions, solar variability, forest fires  Core ages: few years-800,000 years 3 Ice Cores Reading Ice Cores, (8:26 ) Google Images, Ice Cores