Capstone Project for Applied Earth Science Concepts
for Educators in the Context of Polar Regions II
By Tammy Orilio
How do glaciers alter the
landscape?
Pressure from weight of ice + gradual
movement of ice = a changed landscape
 Nearly all erosion on a glacier occurs
along bed & walls and any channel that
contains it

2 Forces of Erosion


ABRASION
Scouring of bedrock
by small, jagged
particles such as
sand grains



PLUCKING
Water from glacier
seeps into fractures
in bedrock, where it
eventually refreezes
Bedrock is now
“bonded” to glacier,
and is yanked with it
as glacier travels
Examples of Erosion Features on
Bedrock…
Striations


Often straight,
parallel scratches on
bedrock
Result from hard &
jagged particles
dragged across
surface of bedrock

Striations are usually found in groupsit’s rare to see just one in the bedrock
 Why do you think that is?
Glacial Grooves
Grooves in bedrock (like striations), but
larger, deeper, and U-shaped
 Often found in weaker zones of rock


Once formed, glacial grooves often
increase in size due to feedback
 The trough-like grooves become a channel
for water to flow through, resulting in more
erosion
Friction/Stress Cracks

Crescent-shaped
cracks often
associated with both
striations & glacial
grooves

May be used to
indicate direction of
glacial flow
 Horn of crescent
points down glacier
Examples of Erosion Features
Associated with Mountains…
U-Shaped Valleys

Mountain glaciers follow the path of
least resistance, which is often a
streambed, ultimately altering the valley
shape
V-shaped river valley

Streambeds tend to
be V-shaped due to
the scouring action
of the water along
with deposition of
sediment on the
inside of the bends
Glacial U-shaped Valley

HOWEVER, the
glacier can’t follow
all the twists & turns
of a stream, so the
bends eventually
erode away, forming
U-shaped valleys
East Fork of the Toklat River, Denali Nat’l
Park- U-shaped Valley!
Hanging Valleys
Results from differing erosion rates b/t a
main glacier and a tributary glacier
 Tributary erodes slower, so the distance
b/t the two glaciers increases over time
 Often results in waterfalls!

Hanging Valley,
Yosemite Nat’l
Park
Cirques

Result from a glacier eroding
horizontally into the side of a mountain
Above the left flank of Midre Lovénbreen is
a un-named well-proportioned cirque glacier
below the peak of Berteltoppen (Svalbard)
Iceberg Lake, Glacier Nat’l Park
Think of an amphitheater- steep sides
(seats) form the back wall, rounded
bottom (stage) opens downslope
 Once ice melts, may leave behind a
cirque lake AKA tarn

Arêtes: & Horns


Arêtes:
Jagged, narrow
ridge formed when
back walls of two
glaciers meet
Matterhorn, Swiss
Alps
Horns:
 formed from multiple
cirques back into
each other
 Think of “squishing”
the mountain from 3
or 4 sides
 Results in a
pyramid-shaped
Striding
Edge Arête,
peak

England
In Conclusion
Abrasion creates the smaller erosional
features, like striations
 Plucking constructs many of the larger,
more “scenic” features
 By analyzing these features, scientists
can learn about glacial extent,
movement, and retreat
