1. HOW GLACIERS MODEL THE LAND
UNIT 11
The evolution of landforms
HOW GLACIERS MODEL THE LAND
Biology and Geology 4. Secondary Education

2. 11 How glaciers model the land
UNIT 11
How glaciers model the land
Glaciers are enormous masses of ice which are formed by accumulation, compaction and re-crystallisation of the snow deposited in very cold (and mostly remote) regions on the Earth's surface.
The ice in the glaciers can flow and, like all moving objects, it has energy which enables it to cause erosion, transportation and sedimentation on the materials that make up the terrain. This enables glaciers to modify the relief.
As it slides along, the ice rips off fragments of rock (erosion).
The fragments of rock are carried to lower areas (transportation).
At the end of its course, the glacier deposits the transported fragments (sedimentation).
Biology and Geology 4. Secondary Education

3. 11 How glaciers model the land Glaciers erode the terrain in two ways:
UNIT 11
How glaciers model the land
EROSION
Glaciers erode the terrain in two ways:
By entrainment: as the ice moves down the slope of a surface with fractures, due to frost weathering, it lifts up blocks of rock of all sizes, which are incorporated into the mass of ice.
By abrasion: the fragments of rock carried by the glacier rub against the surface, smoothing it and polishing it (like sandpaper) or creating grooves called glacial striations, which make it possible to know the direction of movement of the ice after it has receded.
The speed of erosion of the glacier depends on how fast the ice moves, its thickness, the size of the fragments it carries and the type of soil the glacier moves across.
Biology and Geology 4. Secondary Education

4. 11 How glaciers model the land LANDFORMS CREATED BY EROSION
UNIT 11
How glaciers model the land
LANDFORMS CREATED BY EROSION
Once the glaciers have receded, we can identify the following forms of erosion:
• Glacial valleys. They are wide and U-shaped. They transform into V-shaped fluvial valleys as watercourses flow down them.
U-shaped glacial valley
V-shaped fluvial valley
Biology and Geology 4. Secondary Education

5. 11 How glaciers model the land LANDFORMS CREATED BY EROSION
UNIT 11
How glaciers model the land
LANDFORMS CREATED BY EROSION
Once the glaciers have receded, we can identify the following forms of erosion:
• Glacial valleys. They are wide and U-shaped. They transform into V-shaped fluvial valleys as watercourses flow down them.
Terrain after the glaciers have receded
Valley glaciers during glaciation (30,000 years ago)
Biology and Geology 4. Secondary Education

6. 11 How glaciers model the land LANDFORMS CREATED BY EROSION
UNIT 11
How glaciers model the land
LANDFORMS CREATED BY EROSION
Once the glaciers have receded, we can identify the following forms of erosion:
• Glacial valleys. They are wide and U-shaped. They transform into V-shaped fluvial valleys as watercourses flow down them.
• Glacial cirques. They are large depressions which remain in the former area of accumulation of the glacier. They often have lakes.
• Horns and arêtes (or ridges) They are the sharp peaks and crests on the mountains around the cirque, which have been formed by erosion.
• Roches moutonnées They are the rocks on the valley bottom, which have been polished by the glacier.
• Fjords They are former glacial valleys whose final section is flooded by the sea.
Glacial cirques
Horn
Arête
U-shaped valleys
Biology and Geology 4. Secondary Education

7. Transportation of matter by the ice flow
UNIT 11
How glaciers model the land
TRANSPORTATION AND SEDIMENTATION
As the glaciers move slowly, eroding the valleys, they incorporate and transport a large quantity of rock fragments.
When the ice from the glaciers recedes, all those materials are deposited, creating different forms of glacial sedimentation, generally known as tills or tillites.
Entry into the system
Exit from the system
Snow
Evaporation
Transportation of matter by the ice flow
Fusion and drainage
Biology and Geology 4. Secondary Education

8. 11 How glaciers model the land TRANSPORTATION AND SEDIMENTATION
UNIT
TRANSPORTATION AND SEDIMENTATION
As the glaciers move slowly, eroding the valleys, they incorporate and transport a large quantity of rock fragments. 11
How glaciers model the land
When the ice from the glaciers recedes, all those materials are deposited, creating different forms of glacial sedimentation, generally known as tills or tillites.
Tills are an unsorted mixture of angular fragments of different sizes, from sands or gravels to large blocks.
Biology and Geology 4. Secondary Education

9. 11 How glaciers model the land TRANSPORTATION AND SEDIMENTATION
UNIT
TRANSPORTATION AND SEDIMENTATION
As the glaciers move slowly, eroding the valleys, they incorporate and transport a large quantity of rock fragments. 11
How glaciers model the land
When the ice from the glaciers recedes, all those materials are deposited, creating different forms of glacial sedimentation, generally known as tills or tillites.
Tills are an unsorted mixture of angular fragments of different sizes, from sands or gravels to large blocks.
The most common forms of transportation and deposition are moraines, which may be lateral, medial, ground or terminal.
Lateral moraines
Medial moraine
Ground moraine
Terminal moraines
Biology and Geology 4. Secondary Education