FIGURE 11.19 The coast of Norway is known for its many fiords.
Frequently these ice-sculpted inlets of the sea are hundreds of meters
deep. (Satellite images courtesy of NASA; photo by Wolfgang Meier/
Photolibrary)
273
Landforms Created by Glacial Erosion
originate from the same basic process, the enlargement of
cirques produced by plucking and frost action. In the case of
the spires of rock called horns, cirques around a single high
mountain are responsible. As the cirques enlarge and
converge, an isolated horn is produced. The most famous
example is the Matterhorn in the Swiss Alps (FIGURE 11.20).
Arêtes can be formed in a similar manner, except that
the cirques are not clustered around a point but rather exist
on opposite sides of a divide. As the cirques grow, the divide
separating them is reduced to a narrow knifelike partition.
An arête, however, may also be created in another way.
When two glaciers occupy parallel valleys, an arête can form
when the divide separating the moving tongues of ice is
progressively narrowed as the glaciers scour and widen their
adjacent valleys.
Roches Moutonnées
In many glaciated landscapes, but most frequently where continental ice
sheets have modified the terrain, the ice carves small streamlined hills
from protruding bedrock knobs. Such an asymmetrical knob of bedrock
is called a roche moutonnée (French for sheep rock). It is formed when
glacial abrasion smoothes the gentle slope facing the oncoming ice sheet
and plucking steepens the opposite side as the ice rides over the knob
(FIGURE 11.21). Roches moutonnées indicate the direction of glacial flow,
because the gentler slope is generally on the side from which the
ice advanced.
C O N C E P T C H E C K 1 1 . 4
How does a glaciated mountain valley differ in appearance from a mountain valley that was not glaciated?
Describe the features created by glacial erosion that you might expect to
see in an area where valley glaciers recently existed.
2
1
FIGURE 11.20 Horns are sharp, pyramidlike peaks that are fashioned by alpine
glaciers. This example is the famous Matterhorn in the Swiss Alps. (Photo by
Imagebroker/Alamy)
Frequently these ice-sculpted inlets of the sea are hundreds of meters
deep. (Satellite images courtesy of NASA; photo by Wolfgang Meier/
Photolibrary)
273
Landforms Created by Glacial Erosion
originate from the same basic process, the enlargement of
cirques produced by plucking and frost action. In the case of
the spires of rock called horns, cirques around a single high
mountain are responsible. As the cirques enlarge and
converge, an isolated horn is produced. The most famous
example is the Matterhorn in the Swiss Alps (FIGURE 11.20).
Arêtes can be formed in a similar manner, except that
the cirques are not clustered around a point but rather exist
on opposite sides of a divide. As the cirques grow, the divide
separating them is reduced to a narrow knifelike partition.
An arête, however, may also be created in another way.
When two glaciers occupy parallel valleys, an arête can form
when the divide separating the moving tongues of ice is
progressively narrowed as the glaciers scour and widen their
adjacent valleys.
Roches Moutonnées
In many glaciated landscapes, but most frequently where continental ice
sheets have modified the terrain, the ice carves small streamlined hills
from protruding bedrock knobs. Such an asymmetrical knob of bedrock
is called a roche moutonnée (French for sheep rock). It is formed when
glacial abrasion smoothes the gentle slope facing the oncoming ice sheet
and plucking steepens the opposite side as the ice rides over the knob
(FIGURE 11.21). Roches moutonnées indicate the direction of glacial flow,
because the gentler slope is generally on the side from which the
ice advanced.
C O N C E P T C H E C K 1 1 . 4
How does a glaciated mountain valley differ in appearance from a mountain valley that was not glaciated?
Describe the features created by glacial erosion that you might expect to
see in an area where valley glaciers recently existed.
2
1
FIGURE 11.20 Horns are sharp, pyramidlike peaks that are fashioned by alpine
glaciers. This example is the famous Matterhorn in the Swiss Alps. (Photo by
Imagebroker/Alamy)