Glaciers rivers of ice

1. Glaciers - Rivers of Ice How Glaciers Erode Our landscape and change it forever Mr. Spencer

2. What is a glacier? A slow-moving “river of ice” that slowly carves up the land it travels across, forever changing its shape.

3. How do glaciers move? Most glaciers are called ALPINE GLACIERS. That means they start out high up in the mountains, as you can see in this picture, as this one “snakes” its way down the mountain.

4. Glaciers move like pancake batter! Like pancake batter, glaciers spread outward because of the increased mass in the middle. The pressure on top as more snow falls crushes the bottom layer into ice which start to slide across the ground, taking the top layers with it.

5. Glaciers are like sandpaper! As the glacier slides its way slowly across the land, it picks up rocks that make its bottom scratchy, like sandpaper. Along with its HUGE weight, this makes it scratch up the land over thousands of years.

6. Glaciers are vandals! This land was originally flat! Look at what a glacier has done to it!

7. Some glaciers cover whole pieces of land = called ICE SHEETS Greenland, and its GIANT glacier = 2700 meters deep (that’s a lot of meter sticks stacked on top of each other!!!) Ice sheets are also called “ continental glaciers ” because they are HUGE!!!

8. Greenland Ice Sheet from space

9. Another continental glacier Antarctica is a giant rock, covered by a MASSIVE continental glacier!

10. Why are glaciers important They change the shape of the land = most of the places we live in were carved out by glaciers in the ICE AGE. They keep the planet temperature down, like ice cubes in a drink keep it cool on a hot summer day. Problem: They are melting! (more on that later…)

11. Watch your step on a glacier! As the glacier moves over uneven ground, the ice sheet breaks, causing deep cracks, called crevasses.

12. Dangers from below! These can be very dangerous, if they get covered by a sheet of thin ice and you come walking along!

13. HUGE crevasses! Some scientists believe that because of climate change, some crevasses in the Greenland ice sheet may be as deep as the height of five CN towers stacked on top of each other!

14. Looking up from inside a very deep crevass !

15. Ice sheets meet the ocean… Once the ice sheet meets the ocean, the warmer ocean water will cause huge sections of the sheet to break off…

16. …icebergs break off the ice sheet Danger to sea ships – most of the ice is underwater! Ex. Titanic disaster

17. How glaciers shape our land

18. Alpine mountain glaciers – feature #1 – A Cirque = when a glacier carves out a “bowl-shaped” hollow on the side of a mountain, like someone came along with a giant ice cream scoop!

19. Cirque

20. Alpine Mountain glacier Feature #2 – an arete = formed when cirques form on both sides of a mountain = creates a sharp ridge.

21. An arete – can you see the many cirques on both sides?

22. Alpine Mountain glacier Feature #3: a horn When three or more cirques on a mountain weather down all three sides, a pyramid shape peak called a HORN can form – this one is massive!

23. Horn

24. Part 3: Hints that a glacier has passed through your area!

25. Clue #1 – U-shaped valleys During the Ice Age, glaciers scratched up the land, widening valleys to leave them with smooth, round bottoms and steep sides = U-shaped valleys .

26. Clue #2 - Fiords If a U-shape valley is below sea level and reaches the ocean, it will fill up with ocean water = called a fiord Local example: Howe Sound, where Horseshoe Bay is…

27. Clue #3 – Hanging Valleys When a small glacier creates a U-shaped valley above an area carved out by a larger glacier below, we often end up with one valley above the other, and a waterfall.

28. Local Example: Shannon Falls near Squamish

29. Clue #4 - Striations As glaciers move along, they pick up pebbles and rocks – the pressure of their weight leaves “claw marks” on the ground rock surface, called striations

30. Some rock types are so hard, glaciers can’t wear them down… As glaciers move along, they may encounter rock surfaces they cannot weather and erode = go around them

31. Local example: The “Chief” in Squamish

32. Squamish Chief = popular rock climbing rock – can you see the striations on the sides, where a glacier scraped its way along the granite wall?!

33. Clue #5 - Erratics Erratics are giant boulders that are carried by a glacier from somewhere very far away, then left behind when the glacier melted.

34. Erratics look like a giant just dropped them in the middle of nowhere!

35. Local Example: The “White Rock” in White Rock, B.C.

36. Clue #6 - moraines Large ridges of gravel and dirt left at the sides and end of a glacier when it melts = form hills Before: After the melt – see the hills?

37. Clue #7 - Eskers Streams melt off glacier As a glacier melts, little streams of water run off of it, carrying sand and gravel. When these creeks dry up, they leave snake-like mounds that get covered with grass and plants over centuries

38. Esker hill in Ireland

39. Evidence of global warming and climate change = look to glaciers Glaciers that have been around for thousands of years are melting at an alarming rate all over the planet, and are not returning. Just look at this shot, taken from the same exact spot – note the dates!

40. Glaciers are a beautiful example of the natural work, and play an important role in our weather and water systems

41. Glacier shaped like a face = weird!

42. Can you identify the clues of an ice age glacier on this picture of North Vancouver?

43. To review – Identify the glacier features