Landforms and Landscapes of
Continental Glaciation
Objectives
• Delineate and describe contemporary continental ice
sheets and the ice sheets of past glacial periods
• Summarize the history of continental glaciation in
North America, and how our understanding of that
history has changed over time
• Identify typical landforms and landscapes produced by
continental glaciers and discuss the glacial processes
that formed them
• Describe the development of the Great Lakes
• Briefly discuss the pluvial lakes that formed during
glacial periods in the western United State
Ice Sheets, Present and Past
• Peak ice sheets prevailed 21,000 years ago
• Ice sheets have receded steadily ever since
• Today, only two ice sheets persist
1.
2.
Antarctica
Greenland
Map of south-central Alaska
showing possible maximum
extent of most recent Ice Age. ©
USGS
Antarctic Ice Sheet
• Covers much of the Antarctic
continent
• Contains narrow zones of
fast-flowing ice called ice
streams
• Ice shelves are floating
extensions of glaciers
• Chunks of ice break off and
form icebergs through a
process called calving.
The Greenland Ice Sheet
• One-eighth the size of
Antarctica
• Ice Sheets creates
most of the surface of
Greenland
• Contains only about
11 percent of world’s
freshwater supply
Ice Sheets of Late Cenozoic
• North America
– Laurentide Ice Sheet
• largest continental
glacier
– Cordilleran Ice Sheet
• Just west of Laurentide
Ice Sheet
• Extended just south of
USA-Canada border
Image illustrates the extent of the Laurentide Ice Sheet from Canada
east of the Rocky Mountains to as far south as the Ohio River Valley
and southern Illinois.
Ice Sheets of Late Cenozoic
• Eurasia
– Scandinavian Ice Sheet
• Largest continental glacier
• Slightly less extensive than North America’s Laurentide Ice Sheet
Image of the extent
Scandinavian Ice
Sheet centered on
Scandinavian
Peninsula
southward to
central Europe
North America’s Glaciations
• Glacial Periods
– Wisconsinan, Illinoian,
Kansan, Nebraskan
• Named for the area that
provides the best evidence
• Wisconsinan occurred
25,000 and 16,000 years ago
• Illinoian occurred 150,000 to
130,000 years ago
• Interglacial Period
– Sangamonian Soil
• Sits between Wisconsinan
and Illinoian glacial periods
Landscapes Shaped by
Continental Ice Sheets
• Glacial
Sediment/Drift
– Till – poorly sorted
deposits
– Outwash –
meltwater carries
sediments some
distance and sorts
them by particle
size; layered
Glaciated Landscapes
• Hummocky
topography
– Small depressions
• Lakes
– Water-filled
depressions
• Erratics
– Large boulders far
from source
Moraines
• Linear ridge of glacial drift
– Terminal Moraine
• Outermost limit of ice sheet
• Provides evidence of glacial
extent
– Recessional Moraine
• Retreat stalls or minor readvancement of ice sheet
Drumlins
• Smooth, steep-sided, elliptical-shaped mound
• Develops beneath glacial ice
• Lies parallel to the direction of movement
Glacial Meltwater Landforms
Depositional Features
• Esker – under-glacial,
stream channel
• Kame – rounded hill of
sediment
• Kettles – steep-sided,
water-filled
depressions
Glacial Lakes
• The 5 Great Lakes
– Largest cluster of
freshwater lakes
– Basin depth of 223
m (733 ft) below
sea level carved by
glaciers
– Water levels
dependent on
elevation of lowest
outlet and/or
isostatic rebound
Pluvial Lakes
• Water-filled basin
• Not directly caused
by glaciers
• High precipitation
and low evaporation
rates