Chapter 16 Glaciers and Glaciations Name: Page 419-454 (2nd Ed.) ; Page 406-439 (1st Ed.) Part A: Anticipation Guide: Please read through these statements before reading and mark them as true or false. As you read through the chapter correct any false statements so the statement is then true. 1. Immense ice sheets, covering as much as 3/4 of the Earth s land surface had a profound effect on the landscape and civilization. 2. Glaciations only ended about 10,000years ago. Preserved in the rock record, however, is evidence of older glaciations extending back as far as 2.8 billion years. 3. A glacier is a large, long lasting mass of ice, formed on land that moves down slope under the influence of gravity. Glaciers develop anywhere more snow accumulates than melts away or is otherwise lost. 4. Alpine glaciations is found on large part of continents. 5. A continental glacier is found in mountainous regions. 6. Louis Agassiz proposed that there had been an extensive continental glaciations over Europe in the early 1800s. 7. Agassiz s theory eventually would be known as the theory of continental change. 8. he Great lakes, inger Lakes, and thousands of lakes on the Canadian Shield are products of the last glacial age. 9. hick deposits of glacial sediment - more than 200 meters thick in some areas of the southern Prairies - store and transmit large amounts of oil and gas. 10. Glaciers occur both in cold, polar regions where there is little melting in the summer, and in temperate (mild) climates that have heavy snowfall in the cold times and melting in the warmer months. 11. On Baffin Island, the 10,000 year old Barnes Ice Cap and Penny Ice Cap are the only Canadian remnants of the gigantic Laurentide Ice Sheet that covered North America 20,000 years ago. 12. At present 1/30 of the Earth s surface is covered by glaciers. 13. If all of Antarctica s ice melted, global sea level would rise by more than 60m. 14. A valley glacier is a glacier that is confined to a valley and flows from a higher to lower elevation. 15. An ice sheet is a mass of ice that is not restricted to a valley but covers a large area of land (more than 50,000 km 2 )
16. Similar to an ice sheet, an ice cap is the same idea but simply smaller. 17. Snow coverts to glacier ice in somewhat the same way that sediment turns into sedimentary rock and then into metamorphic rock. 18. he compacted mass of granular snow, transition between snow and glacier ice is called talus. 19. Under the influence of gravity ice moves downward and is eventually ablated. 20. In the coldest parts of the world the most melting is through evaporation. 21. Advancing glaciers are glaciers with negative glacial budgets, where more ice is gained than lost in a year. 22. Glacial ice moves downvalley only if it is a receding glacier. 23. he upper part of a glacier is called the zone of ablation. 24. he lower part of a glacier, below the equilibrium line, is known as the zone of accumulation. 25. An equilibrium line moving upglacier over a period of years is a sign of an advancing glacier. 26. he lower end of the glacier is known as the moraine. 27. It is estimated that a worldwide decrease in mean annual temperatures of about 5 C could bring about a new ice age. 28. Velocity of moving ice varies within the glacier itself. 29. When sliding takes place as a single body over the underlying rock, basal sliding is taking place. 30. During glacial flow, movement that shows deformable behavior of ice is called plastic flow. 31. Cracks or fissures in a glacier is known as a scarp. 32. Ablation in Antarctica is largely through calving (breaking off) of icebergs. 33. At the south pole there is 6,700m of ice. 34. he process known as plucking occurs when pieces of rock are broken loose and frozen into the base of a moving glacier. 35. Abrasion is the least active on the up-ice side of bedrock irregularities where pressures are high. It is the process by which a glacier grinds away at the underlying rock. 36. Rock flour is composed of very fine (silt, clay) particles of unaltered minerals.
37. Not all glacier associated erosion is caused directly glaciers. Mass wasting takes place on the steep slopes created by downcutting glaciers. 38. runcated spurs have steep bedrock walls and a relatively flat floor. he flat floor is usually formed by bedrock but it is underlain by glacial and fluvial sediments that overlie a very irregular bedrock surface. 39. Glacial erosion of ridges that formerly extend into the valley creates glacial troughs. 40. he amount of eroding a glacier does is not dependant on ice velocity, ice mass, and the nature of basal debris. 41. Large trunk glaciers do not carve as deep as the smaller tributary glaciers that join them. hese small tributary glaciers leave features called hanging valleys. 42. A glacial lake (or lake caused by a glacier) is called a Jökulhlaup. 43. Areas where bedrock is relatively resistant to erosion form roches moutonnées, streamlined bedrock knobs elongated (made longer) parallel to glacier flow. 44. A cirque is a sharp peak caused by a glacier. 45. A horn is a sharp peak that remains after a cirque have cut back into a mountain on several sides. 46. Ice sheets tend to scour and smooth the pre-existing landscape, rather than deeply dissecting it. It is estimated that, on average, only 350m of material was eroded from the Canadian Shield during all of the Quaternary glaciations combined. 47. Ice sheets can be up to 4,000 meters and in many places completely blanket the terrain. 48. he unsorted and unlayered rock debris carried and deposited by a glacier is called tarn 49. Glaciers are capable of carrying virtually any size of rock fragment, even boulders as large as a house. An erratic is an ice-transported boulder that has not been derived from underlying bedrock. 50. Low mounds of debris that form along the sides of a glacier are called lateral moraines. An actively flowing glacier brings debris to its terminus. If the terminus remains stationary for a few year or advances, a distinct end moraine, a ridge of glacial debris. 51. A till plain, a fairly thin, extensive layer or blanket of bedrock. 52. A drumlin is shaped like an inverted spoon aligned perpendicular to the direction of ice movement.
Part B: Short Answer and Application 1. What is the theory of glacial ages? 2. Using the table below, show what the difference between an alpine glacier and a continental glacier. Alpine Glacier Continental Glacier 3. How does fresh snow eventually become glacial ice? Note: Granular snow is sometimes referred to as névé (snow that has been around for 1 or 2 winters without melting. It will then turn into firn
4. Define the following: (a) zone of accumulation: (b) zone of ablation : (c) equilibrium line: 5. Using igure 16.8 (2nd edition, Page 426 or 1st Edition Page 414) explain how Drill holes explain the motion a glacier takes specigically rigid zone, plastic zone, basal sliding
6. What is a crevasse? 7. How do glaciers cause erosion? Discuss plucking, abrasion, polishing and striations and meltwater. 8. Label Me!
9. What is an erratic and what can it tell you about the glacier that deposited it? 10. Label this diagram (igure 16.25) 11. Define the following: (a) Moraine: (b) Lateral Moraine (c) Medial Moraine (d) End Moraine (e) till plain:
12. What is a drumlin? Application Questions 13. As you move around Nova Scotia, what features discussed above can you observe that show us that a glacier was here at one time? 14. A friend of yours tells you that glaciers are constantly retreating. Do you agree or disagree with them and why? 15. Do you agree or disagree with the following statement: Humans have sufficient technology to survive the next ice age? 16. How would you identify whether a rock was an erratic or not? Explain yourself.