Chapter 15: Glaciers and Glaciation
OBJECTIVES
•
Explain the formation and movement of glacier ice.
•
Describe the process of glacial erosion and the landforms
that glacial erosion produces.
•
Describe the processes of glacial deposition and the effects
glaciers have on Earth’s landscape.
•
Describe the influence of the Pleistocene ice age on the
landscapes of the northern hemisphere.
OBJECTIVES
•
Summarize the evidence that is used to deduce the
existence and causes of ancient ice ages.
•
List other instances of glaciation from across our Solar
System.
Glacial Ice
• A glacier forms on land and is
heavy enough to flow under
its own weight.
• Firn, a granular variety of ice,
forms when snow crystals are
compacted.
• As firn is compressed, it forms
glacial ice.
Fig. 15.1
Glacial Growth
• Glaciers grow when accumulation exceeds ablation.
• Glaciers shrink when ablation exceeds accumulation.
Fig. 15.6
Types of Glaciers
• Continental glaciers cover an entire landmass.
• Alpine glaciers form at high altitudes.
Figs. 15.3a, Fig 15.4
How Glaciers Move
• Plastic flow occurs when ice crystals change shape.
• Basal sliding occurs when the glacier slides along its base.
Fig. 15.5
Continental Glacial Erosion
• Continental glaciers produce striations as well as roches
moutonées.
Striations
Roche moutonée
Figs. 15.7, 15.8
Alpine Glacial Erosion
• Erosion by alpine glaciers produces a variety of landforms.
Fig. 15.10
Glacial Deposition
• Glaciers transport large amounts of sediment.
• Glacial sediment can be deposited by ice or meltwater.
• Sediment deposited by a glacier is known as glacial drift.
Fig. 15.17
Types of Moraines
Figs. 15.19, 15.20
Meltwater Deposits
• Stratified drift, outwash plains, kettles, kames, and eskers
form as a result of glaciers melting.
Fig. 15.24
The Pleistocene Ice Age
• During the Pleistocene
Epoch, glaciers covered
much of North America.
• The Pleistocene ice age
had effects on sea level
and topography.
Fig. 15.28
Pluvial Lakes
• Pluvial lakes form as a
result of increased
precipitation and
reduced evaporation.
• Some modern landforms
in the southwest United
States are former pluvial
lakes.
Fig. 15.29
Glacial Modification of Drainage
• The Pleistocene glaciation significantly changed drainage in most
of North America.
Fig. 15.32
Plate Tectonics and Glaciation
• Continental positions and plate tectonic motions can affect
global climate and lead to glaciation.
Fig. 15.37
Ice on Other Worlds
• A number of other bodies in the Solar System, including
Europa and Mars, have ice on or below the surface.
Figs. 15.39a, 15.40
Summary
• Glaciers
• Form when snow becomes compacted and begins to
flow under its own weight
• Move via plastic flow and basal sliding
• Can produce distinctive landforms through erosion and
deposition
• Covered a much larger portion of Earth’s surface during
the Pleistocene Epoch
• Produced many of the distinctive topographic features
in North America
• May be found on other bodies in the Solar System in
addition to Earth