4th agent of erosion is Glaciers
Glaciers
• Glacier – a large mass of moving ice and
snow. Forms where there are large
snowfalls and temps remain cold.
• Glacial ice erodes through abrasion or by
plucking away at the rock beneath it. One
of the most powerful agents of erosion.
Deposits by Glaciers
• Till – rocks and soil
deposited by a glacier.
Particles vary in size and
are not sorted.
• Moraines – formed when
a glacier melts and
retreats leaving a ridge of
till.
• Terminal moraine –
deposited at the front.
• Lateral moraine – till
deposited along the
sides.
Terminal and Lateral Moraines
Glacier Terminology
Glacier deposits continued…
• Drumlins – an ovalshaped mound of
till. The tip points in
the direction the
glacier was moving.
• Meltwater –
streams formed by
melting ice.
Still more…
• Icebergs – when part of the
glaciers break off and drift into
the sea.
• Glacial lakes –holes left by
glaciers fill with water. Ex: The
Great Lakes of Michigan, The
Finger Lakes in New York.
• Kettle lakes – when a huge
block of glacial ice is left behind
and melts to form a deep round
hole that fills with the water
from melting.
The Great Lakes
LAKE HURON
th
5
agent of erosion is Waves
• Under normal
conditions, waves
erode about 1 to 1.5
meters per year.
• During storms it is
increased up to 25
meters per day.
Wave Erosion cont.
• Sea cliffs- a steep face of
rock .
• Terrace – when a sea cliff
is erodes and a buildup
or rocks and sand form a
flat platform.
• Sea stack – a column of
resistant rock left
standing.
• Sea cave – when wave
action erodes rock and
forms a cave.
Deposits by Waves
• Beaches - eroded rock particles
are deposited on a shoreline,
may vary in materials. Ex:
Atlantic coast has white sand,
Hawaii has black sand, and so
on.
• Long-shore current- the
movement of water parallel to
the shoreline.
• Sand bars –a long, underwater
ridge of sand forms from the
long-shore current.
• Spit – forms if the sand bar is
connected to the shoreline.
Sand bar vs a Spit
Sand bar
Spit
• Shape of the shoreline - often results from
changes in the sea level. If it suddenly
drops then there will be many sea cliffs and
terraces; if it rises then there will be many
bays and harbors.