1. Chapter 18: Glaciers

2. Introduction Glacier: thick mass of ice that originates on land from the accumulations, compaction and recrystallization of snow Glaciers are part of two basic cycles Hydrologic cycle Rock cycle Types of Glaciers Valley Glaciers Icesheets Glacier: thick mass of ice that originates on land from the accumulations, compaction and recrystallization of snow Glaciers are part of two basic cycles Hydrologic cycle Rock cycle Types of Glaciers Valley Glaciers Icesheets

3. Valley Glaciers AKA Alpine Glaciers Form in mountainous regions Flow down a valley from an accumulation center at its head AKA Alpine Glaciers Form in mountainous regions Flow down a valley from an accumulation center at its head

4. Icesheets AKA Continental Icesheets Larger scale than Valley Glaciers Flows out in all directions from one or more snow accumulation center Antarctic icesheet is 14 million sq. km. ~1.5x area of United States AKA Continental Icesheets Larger scale than Valley Glaciers Flows out in all directions from one or more snow accumulation center Antarctic icesheet is 14 million sq. km. ~1.5x area of United States

5. If all the ice melted …

6. Transformation of Glacial Ice Removal of air Recrystallization Melting & condensation

7. Movement of Glaciers Basal sliding AKA Basal slip Internal flow AKA Plastic flow Rates ~ m/day Basal sliding AKA Basal slip Internal flow AKA Plastic flow Rates ~ m/day

8. Zone of Fracture Upper 50 m of glacial behaves in brittle manner When glacier moves over irregular terrain, ice under tension Crevasses form Upper 50 m of glacial behaves in brittle manner When glacier moves over irregular terrain, ice under tension Crevasses form

9. Formation of Icebergs

10. Budget of a Glacier Advancing glacier: when accumulation > ablation Retreating glacier: when accumulation < ablation

11. Glacial Erosion Glacial erratic Striations

12. Glaciated Topography

13. Landforms Created by Glaciers

14. Glacial Deposits Glacial Drift: sediments of glacial origin Till: materials deposited directly by the glacier Stratified Drift: sedimentas laid down by glacial melt water Glacial Drift: sediments of glacial origin Till: materials deposited directly by the glacier Stratified Drift: sedimentas laid down by glacial melt water

15. Glacial Till

16. Landforms Made of Till Glacial Erratics: boulders lying in till of lying free on the surface Lateral Moraine: ridge of till paralleling side of valley Medial Moraine: formerly a lateral moraine of a tributary glacier, now in the middle of the glacier End Moraine: ridge of till that forms at the terminus of the glacier Ground Moraine: gently rolling layer of till deposited as the ice front recedes Glacial Erratics: boulders lying in till of lying free on the surface Lateral Moraine: ridge of till paralleling side of valley Medial Moraine: formerly a lateral moraine of a tributary glacier, now in the middle of the glacier End Moraine: ridge of till that forms at the terminus of the glacier Ground Moraine: gently rolling layer of till deposited as the ice front recedes

17. Glacial Depositional Features

18. Glaciers of the Past Last Ice Age: 18,000 years ago Covered 30% of Earth’s land area Four major Ice Ages in North America Nebraskan Kansan Illinoian Wisconsinan Last Ice Age: 18,000 years ago Covered 30% of Earth’s land area Four major Ice Ages in North America Nebraskan Kansan Illinoian Wisconsinan

19. Maximum Extent of Ice During Ice Age

20. Causes of Glaciation Milankovitch cycles EccentricityObliquity Precession 1000,000 yr41,0000 yr26,000 yr Milankovitch cycles EccentricityObliquity Precession 1000,000 yr41,0000 yr26,000 yr

21. Glaciers in Antarctica

22. Mt. Howe: Most southern outcrop of rock Elevation = 9669 ft Ice elevation ~9000 ft Mt. Howe: Most southern outcrop of rock Elevation = 9669 ft Ice elevation ~9000 ft