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A Closer Look: Glacial Landforms
What are examples of landforms created by glacial erosion?
As a glacier
moves, it picks up rock pieces from the landscape. Debris of
all sizes that is stuck in the glacial ice can scour and erode
the land. From this action, valleys can become wider and deeper,
forming u-shaped (or trough) valleys. Glaciers can carve bowl-shaped
depressions, called cirques, into a mountainside. A tarn is a
lake that forms by
ice melting in a cirque. An arête is the steep ridge that forms
between two adjacent cirques. A col is a low spot on an arête.
A horn is a peak formed when three or more adjacent cirque
glaciers carve away the side of a mountain.
Continental glaciers
scour linear finger lakes out of pre-existing stream channels.
Paternoster lakes are a series of lakes that
form in the low spots of a u-shaped valley; a stream that
flows through the valley
links them.
What are some landforms created by glacial deposition?
A glacier will
deposit rock chunks along the sides and the front of it. Moraines
are created when a glacier pushes or
carries along this rock debris as it moves, and then deposits
it. Moraines
can form in front
of a glacier (terminal or end moraine) marking the furthest
position of advance of an ice sheet; along the side of
a glacier (lateral moraine);
or under a glacier (ground moraine). When two glaciers
flow next to each
other they deposit lateral moraines between them called
medial moraines. Long Island, New York and Cape Cod, Massachusetts
are examples of terminal
moraines of the ice sheet that covered New England and
eastern Canada during the last ice age.
Cape Cod, Massachusetts
Drumlins are elongated
hills formed of till (an unsorted mixture of mud, sand, pebbles
and rock deposited by a glacier)
with a distinctive streamline shape that results from
having been overridden
by a glacier
or modified by meltwater. The long axis of a drumlin
indicates the direction of glacier flow. Eskers are the deposits
of
rivers and streams
that flowed
on, in, or under a glacier. They form mounds or hills
that meander across a landscape roughly parallel to the path
of the original glacial
river.
Kettle holes are formed by blocks of ice that separate
from the main glacier. Under the right conditions the
ice blocks will melt and
leave behind holes
or depressions that fill with water to become kettle ponds
or
kettle lakes.
Kettle pond on Cape Cod, Massachusetts
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