Transcript Erosion by Glaciers - Teachers TryScience

Erosion and
Deposition by
Glaciers
Created By:
Belinda Schmahl
Table of Contents
1.
2.
3.
4.
5.
6.
7.
8.
Glaciers Defined
Formation of Glaciers
Valley or Alpine Glaciers
Continental Glaciers or Ice Sheets
Glacier Movement
Glacial Deposition
Landforms caused by Glacial Deposition
Landscape Features
Roughly 18,000 yrs ago 30% of the earth’s surface was covered by glaciers.
This period is known as the GREAT ICE AGE
1. Glaciers Defined
A large mass of ice,
formed on land by the
compaction and
recrystallization of
snow, that is moving
downhill or outward
under the force of
gravity.
 Formed when
snowfall > than rate
of melting

2. Formation of Glaciers

Form when average
incoming snowfall>
than avg. amount lost
by melting and
evaporation Snow
increases each year
– Picture A- Formation
– Picture B- Growing
– Picture C- Retreating
2. Formation of Glaciers cont..

As snow increases and
evaporation occurs ice
crystals become rounded
forming granular snow.

As more snow falls
(alternating melting and
refreezing compacts snow
into a layer called firn
grows into solid ice.
SNOWLINE
6,000m
5,000m
4,000m
3,000m
2,000m
1,000m
Sea Level
North Pole
75N
60N
45N
30N
15N
Equator
This diagram shows how the elevation of the snowline changes
with latitude. The approximate elevation of the snowline is
indicated on this diagram by the white line.
3. Valley or Alpine Glacier

Gravity pulls downward and outward on
bottom layers

This type of glacier carves a U shaped
valley.
***Remember streams carve a V shaped valley
U-Shaped Valley
4. Continental Glacier or Ice Sheets
These are very old and thick and may
cover entire land masses, snow is close to
sea level
 Moves very slowly because of weight
 When it reaches ocean it can break off
Icebergs (called Calving)

– Greenland- 1.7 million square Km (3 Km thick)
– Antarctica- 12.5 million square Km (5 Km
thick)
Depth of Greenland & Antarctic Ice Sheets
5. Glacier Movement

Stationary Glacier- When rate of
movement = rate of melting

Winter- Glacier moves more (WHY???)

Summer Glacier moves less and appears
to move backwards (WHY???)
6. Glacial Deposition

The sediment that is deposited by glaciers
is unsorted (Called Glacial till)
*Remember that sediment deposited by water
is sorted.

If sediment is transported by melt water
of glacier than it is deposited the same as
a river would deposit (Sorted)Outwash
Glacial till - unsorted
7. Landforms caused by Glacial
Deposition
Moraines- Unsorted Sediment along the edge of the
glacier.
 Terminal Moraine-The furthest point of the glacier (Long
Island)
 Erratic- A large rock that looks misplaced
 Drumlins- Long smooth hills of glacial till, points in
direction of glacier movement.
 Karnes- melt water from top of glacier
 Kettles- Circular lakes-Ice breaks off and melts
underground
 Moraine Dammed lake- When a glacial moraine blocks a
river valley, resulting in a long narrow lakes. (Finger
lakes)

Moraine/Terminal Moraine
Erratic
Drumlins
Outwash Plains
Karnes
Kettle Lake
Moraine Dammed Lake
8. Landscape Features
Cirques- Semi circular shaped bedrock
formed as glacier moves back toward
mountain.
 Arêtes- Steep sided bedrock formed as
glacier retreated in opposite direction.


Horns- Where three arêtes meet up
Arête
Cirque
U-Shaped
Valley
Kettle Lake
Drumlins
Esker
Till
Moraine-dammed lake
Terminal Moraine
Glacial Stream