1. Glaciers

2. Groundwater

3. Question of the week What is confined aquifer?

4. Glaciers Moving body of ice that forms from the accumulation and compaction of snow Flows downslope or outward under the influence of gravity and the pressure of their own weight Cover ~10% of the world’s land surface High latitude (at the poles): any elevation, even sea level Mid-latitude: only forms at high elevation

5. I.Glacier Formation A. How? Snow falls and accumulates  light and fluffy or heavy and wet As more snow falls, the weight of overlying snow melts some of the contact points between crystals Water migrates to low pressure areas and refreezes, binding flakes together Creates ice

6. I. Glacier Formation B. Where? 1. Forms when snow accumulation exceeds snow loss due to summer melting Accumulation > summer melting High snow accumulation in winter and then a short or relatively cold summer 2. Above snowline: lowest topographic limit of year- round snow cover

7. I. Glacier Formation B. Where? 3. North-facing slopes more likely, in northern hemisphere South-facing in southern hemisphere - opposite direction of the sun 4. Leeward side of mountain (not the windy side)

8. I. Glacier Formation B. Where? Elevation, precipitation, and aspect

9. I. Glacier Formation B. Where? Above snowline North-facing slopes Leeward side

10. II. Classifying Glaciers Based on whether the local topography confines then or whether they’re allowed to flow freely A.Alpine Glaciers B.Continental (ice sheets) glaciers

12. Valley Glacier

13. Icecap

14. Tidewater Glacier

15. II. Classifying Glaciers Based on whether the local topography confines then or whether they’re allowed to flow freely A. Alpine Glaciers Confined by surrounding bedrock highlands 1.Cirque glaciers: create and occupy semi-circular basins on mountainsides 2. Valley glaciers: flow in preexisting stream valleys 3. Ice caps: form at the tops of mountains, completely bury the underlying landscape

16. ?? Glacier

18. Icecap

19. Tidewater Glacier

22. II. Classifying Glaciers B. (Continental) Ice sheet Completely unconfined Much larger scale glacier Blankets all of the underlying landscape except for the highest peaks Flow out in all directions 2 continental ice sheets: Antarctica & Greenland Greenland average thickness = 5000’, maximum thickness is 10,000’ Antarctic sheet up to 3 miles thick in places!

25. III. Glacier Flow A. Mechanisms 1. Internal Deformation (plastic flow) Ice is brittle until it’s under the pressure of ~165 feet of ice, then it behaves plastically Crevasses are the large cracks at the surface never >165 ft deep Planes of atoms within the ice structure will slide past one another Stress > bond strength between ice crystals

26. III. Glacier Flow A. Mechanisms 2. Basal Sliding Base of glacier is partially melted Water acts as a lubricant

27. III. Glacier Flow B. Rate of Flow Warmer = faster flow 1000” or more a year Cold = slower flow A few meters a year Depends on: thickness & gradient as well High basal fluid pressures = surging glacier (meters/hour)

28. IV. Anatomy of a glacier A. Zone of Accumulation Blanket of snow survives summer melting Nourished by snowfall

29. IV. Anatomy of a glacier B. Zone of Ablation Snow and ice melt & sublimate in summer Recognized by bare ice in summer Where the glacier flows into water: Calving: ice chunks break off and float away  icebergs

30. IV. Anatomy of a glacier C. Equilibrium Line = Snow Line Line that separates the two zones Can change year to year, climate variations

31. IV. Anatomy of a glacier D. Terminus Toe of a glacier

32. Snowfall vs Melting & Evaporation (Ablation) Zone of Accumulation Snowfall Exceeds Melting & Evaporation Excess Snow Turns to Ice & Flows Out Zone of Melting or Ablation Melting & Evaporation Exceeds Snowfall Melting Excess Made up by Ice Flowing in Terminus of Glacier Snowfall & Inflow = Melting & Evaporation (Ablation)