1. glaciers & glaciation Types of glaciers How do glaciers move?
Glacial landforms
Causes of glaciation

2. types of glaciers: valley or alpine glaciers
found in mountainous regions
flow in valleys that were previously occupied by rivers
Frequently merge with other valley glaciers
Lengths vary from less than a kilometer to tens of kilometers
Highly effective as erosional agents

3. Continental ice sheets
What’s it like to be on a continental ice sheet?
Here’s a typical view.
These ice sheets develop in part due to the low levels of solar radiation reaching the Earth’s polar regions. (It’s COLD!)
Continental ice sheets cover about 10% of Earth’s land area.
In general, the ice is thickest near the center of the ice sheets and flows outward in all directions from there.
Where ice flows over ocean water ice shelves are formed.
Shelves become thinner seaward and often break off forming icebergs.
Ice shelves are sustained by ice from the mainland as well as freezing seawater from below.

4. ice sheets on Antarctica & Greenland

5. What would happen if the ice melted?
Glaciers and ice sheets contain 2% of the world’s total volume of water (fresh plus salt). Ice sheets contain over 2/3 of the world’s fresh water. If they melted, sea level would rise meters! Consider what would happen to coastal regions and the major metropolitan areas located near them.
What would happen if the ice melted?

6. What does that mean in the United States?

7. It all starts with a few snowflakes
Here are some glacialogists collecting samples. The snowflakes shown are photographed shortly after they fell and accumulated on the glacier.

8. Step 2: conversion of snowflakes into firn
Is this an SEM image of firn or ice worm eggs
Cross sectional view showing layers of snow and firn in a snow field.
Illustration on left shows density of snow, on right density of firn.
What do you think a picture showing the density of ice would look like?

9. What does glacial ice look like?
Is glacial ice a mineral?
Solid?
Naturally occurring?
Inorganic?
Definite composition?
Definite internal structure?
Glacial ice is interlocking crystals of solid H2O that form once the ice and snow thickness reaches 50 m
Note the growth patterns in the glacial ice above

10. What makes glaciers and ice sheets flow?

11. Is a glacier homogenous throughout it’s depth?
Upper 40 meters forms the rigid zone
Crevasses form here as glacier stretches to flow over bumps in a valley
What is the maximum depth of a crevasse?

12. Characteristics of the plastic zone
The plastic zone begins at a depth of 40 m
Bonds between layers of ice are weaker than those within a layer, thus the layers flow over each other
Basal slip also contributes to the movement of a glacier
Melt water lubricates the bedrock allowing the glacier to slip down the valley

13. How fast do glaciers flow?
Flow rates vary considerably from one glacier to another
Ex. Byrd Glacier, Antarctica has flow rates of about 2 m per day
Flow is often not smooth and continuous
Surges occur, rates of up to 100x normal may occur

14. Glacial budgets
Zone of accumulation is separated from zone of ablation by equilibrium line or snowline
zone of accumulation amount of snowfall is greater than melting on an annual basis
Zone of ablation (wastage) melting is greater than snowfall on an annual basis
Glacial budget is the balance between accumulation and ablation

15. The roar of the thunderous calving of a glacier
Glaciers and ice sheets waste in two ways, melting and calving
Calving is the breaking off of large pieces of ice at the glaciers terminus
Calved pieces form icebergs where the glacier reaches the sea or a lake

16. How do glaciers alter landscapes?
Glaciers alter landscapes significantly in two ways
Glacial erosion creates many new features
Glacial deposition also creates new landscapes
Let’s look at some of the features created by glaciers

17. How do glaciers erode? plucking
Plucking occurs when glaciers flow over fractured bedrock
Loose rock is then incorporated into the ice
Frost wedging increases the effectiveness of plucking
Glaciers aren’t too particular about the size of the sediment transported
In the illustrations we see a boulder about to be plucked and a slope that shows evidence of plucking

18. How do glaciers erode? abrasion
Ice containing sediment acts as sandpaper as it flows over bedrock
Striations are long grooves or scratches created as ice flows over bedrock

19. Landforms associated with glacial erosion
arête & truncated spur
glacial trough
hanging valley

20. Erosional features
horn, cirque, arête
pater noster lakes

21. Erosional features
tarn lake in a cirque
col, cirque, arêtes

22. Erosional features
roche moutonnee
fjord
horn

23. Glacial drift
All sediments of glacial origin are collectively known as glacial drift
Two categories of drift
Till – sediment directly deposited by glacier
Stratified drift – sediment deposited by glacial melt water

24. Glacial till & glacial erratics
Deposited directly by glacial ice
Poorly sorted
Grains often show evidence of abrasion
Erratics – boulder sized grains deposited directly by glacial ice

25. valley/alpine glaciers: moraine deposits
Glacial ice erodes the valley walls incorporating large volumes of rock debris to the edges of the ice
When the ice melts, this debris is deposited along the valley walls forming lateral moraines

26. medial moraines
When two tributary glaciers merge, their lateral moraines merge to form a central medial moraine
By counting medial moraines, glaciologists can determine the number of tributary glaciers that have merged to create a larger glacier

27. terminal, end or recessional moraines
A ridge of till that is deposited at the terminus of a glacier or ice sheet during a time when the glacier is in equilibrium (ablation equals accumulation)
Terminal or end moraines are only different from recessional moraines in that they mark the furthest extent of a glacier’s terminus

28. Terminal, end or recessional moraines

29. ground moraines
A relatively flat layer of till deposited as the terminus of the ice recedes
Ground moraines tend to level the surface, filing in depressions and clogging stream channels
They are common with either valley/alpine glaciers or ice sheets

30. drumlins Hills of glacial till deposited by a glacier or ice sheet
Range in height from 15 to 50 meters
May be up to 1 km long
Oblong in shape
Steeper side faces the direction the ice advanced from, gentler slope points direction ice flowed toward

31. Landforms of stratified drift
Glacial meltwater sorts and deposits sediment
Commonly sand & gravel sized grains
Rock flour is transported as suspended load
Outwash plains are associated with ice sheets
Valley trains are associated with valley glaciers
Broad, flat surface covered with stratified drift deposits

32. Kettle lakes, kames, eskers
Kettle lakes form when blocks of ice remain lodged in drift and eventually melt in the depression they formed
Eskers are ridges deposited beneath glacial ice by sub- glacial streams