Geology Reference
In-Depth Information
Drumlins
When a large glacier or ice sheet advances over pre-existing moraines (from the earlier
advance and retreat of glaciers), the original till deposit will be reshaped by erosion into
rounded, elongated hills called
drumlins.
The narrow, pointed end of the drumlin (shown
in upcoming Figure 13-5) points in the direction of the ice flow that shaped it. Drumlins
created by ice sheets often occur in groups, or
drumlin fields,
with hundreds of drumlins
scattered across the landscape.
Plains, trains, eskers, and kames
Stratified glacial deposits
occur when sediment is removed from the glacial ice by melt-
water in the form of streams. The streams originate in or on the glacier as it begins to
melt, usually near the end of the glacier. The meltwater flows farther downhill, beyond
the terminus of the ice.
Deposits left behind by meltwater are well-sorted because they are transported by wa-
ter. They are deposited by size (the largest settling first) in layers or strata. Landscape
features made of stratified deposits are composed of particles small enough to be car-
ried by water, such as sand or clay (I describe grain sizes in Chapter 7). Figure 13-5 illus-
trates the landscape features I describe in this section.
Figure 13-5:
Features of glacial
deposition.
