Transcript AIM: How do Glaciers change the landscape?

AIM: How do Glaciers change the landscape?
Do Now: As a bulldozer moves over the land, describe what
happens to the ground as the shovel moves across it. Then
describe what the pile of sediment looks like after the bulldozer
moves away
Perito Moreno Glacier, Argentina
I. Types of Glaciers
Thick masses of ice that form
over hundreds or thousands of
years.
• Valley Glacier: a stream of ice that
flows between steep rock walls
(valleys).
•Ice Sheets: also called continental ice
they flow in all directions covering the
land.
II. Glacial Movement
- Glacial movement is called
• Glaciers advance when they
accumulate (gain) more ice from
freezing at the glaciers head. They
also slide very slowly down hill due
to gravity.
• Glaciers retreat when they lose
more ice from pieces falling off or
melting.
III. Glacial Features
A. Erosion
- Glaciers cut “Ushaped” valleys
through the
ground. These
form in glacial
valleys
- Erosion also
creates Cirques,
Arêtes and Horns.
• Plucking and Abrasion
- Plucking- when glaciers loosen and lift up rocks
from the surface.
- Abrasion- rocks trapped in the glacier grind against
rocks on the surface as the glacier moves. This
creates scratches and grooves in the bedrock, called
striations.
B. Deposition
-Glaciers create till, which is
unsorted sediment deposited
by the glacier.
-Deposition also creates
kettles, outwash plains and
moraines, which are ridges
of unsorted of till.
-Glacial Erratic are large
boulders left behind from
melting glaciers
IV. Glaciers and Long Island
• The red on Long Island and Connecticut indicates two
moraines formed by two different glaciers. The first
ended about 21,000 years ago and formed the
Ronkonkoma moraine (South Shore). The second,
ended about 10,000 years ago and formed the Harbor
Hill moraine (North Shore).
Closure
•Obtain a worksheet on Glaciers. With the
person sitting next to you use the notes to
answer the questions on the handout.
•You have about 5 min to work on it
How do Glaciers Change the
Landscape? - Worksheet
1.
Ice Sheets
• Thinner, flat
expanse of ice
•Covers
continents and
can extend out
into oceans
•Also called
continental ice
Glacial Valley
•Creates “UShaped” trough
•Moves between
two mountains
(steep rock)
•Occurs only on
continent
2. Plucking is when glaciers loosen and pick
up rock off the surface of the Earth. Abrasion
occurs when rocks trapped in the glacier
grind against rocks on the surface of the
Earth.
3.
It was created by
a glacier because
of the “U-shaped”
valley that was
created
4. Over the last 25,000 years glaciers have
shaped the land in New York. Glaciers
advance when they freeze more water than
melts away. At two different times glacial
advances plucked sediment out of the ground
and moved it South. During glacial retreats,
when more water melts than freezes, the
sediment was left behind to form two
moraines. These moraines later became the
North and South shores of Long Island.
AIM: How does Wind change the Landscape?
Do Now: In your notes, describe how a sand blaster
works. If your not sure, ask the person sitting next
you. Then describe how nature could create “ a sand
blaster”. What would you need?
Namib Desert of Namibia, Angola
I. Wind Erosion
• Wind erosion is most effective in deserts.
• Strong wind erodes great quantities of
fine sediment leaving coarse sediment
behind.
A. Deflation: occurs when wind lifts and
removes loose particles like silt and clay.
Larger particle skip and roll along the
surface.
B. Abrasion: occurs when wind blown
particles cuts and polishes exposed rock
acting like a sand blaster.
Double Arch, Arches National Park Utah
II. Wind Deposition
- Wind creates deposits of sediments that are sorted (graded).
 As energy is lost, larger
particles are dropped first.
Smaller particles are
on top
Larger particles are on
the bottom
A. Loess: windblown silt
that blankets the
landscape.
B. Sand Dunes: are mounds or ridges of sand that are created
when wind blown sand encounters and obstruction.
- Sand dunes have a gentle slope on the side the wind is
blowing from, windward side. The side that is sheltered
from the wind is at a steeper slope, sheltered side.
WIND
 Crossbed – sloping layers caused by sand
being deposited on the sheltered side of a
dune. Lithification turns this sediment into
sedimentary rock and the crossbeds are
still seen.
Closure
•Obtain a worksheet on Wind. With the
person sitting next to you use the notes to
answer the questions on the handout.
•You have about 5 min to work on it
1. Wind pushes
sediments up
gently along the
slope facing the
wind. Sediment
falls off the other
side creating a
steeper slope.
WIND
2. Deflation lowers the land removing necessary
soils for farmers to grow their crops in.
3. There is nothing to block the wind and there
is an endless supply of sediments to move
around.
4. How should the sediment
look after it was transported by
the wind?
AIM: How do waves
shape the Shoreline?
Do Now: In your notes
answer the following
questions. Think about the
times you were at the beach.
Maybe you built a sand castle
near the shore line. What
would the waves do to your
castle? Describe in detail he
sequence of events that
occur after you built your
castle and the waves come
in.
I. Forces acting on the Shoreline
- Waves constantly erode, transport and deposit
sediment along the shoreline.
- Storms increase the activity of waves.
A. Longshore Drift: occurs when currents flow parallel to
the beach and carry large amounts of sediment.
- This current easily moves fine sediment and rolls larger
sediment along the bottom.
II. Wave Erosion
- Waves constantly remove sediment from
the shore line.
-Wave action causes abrasion to occur
forming Sea Arches and Sea Stacks
III. Wave Deposition
- The accumulation of sediment along the shore is called the
beach.
A. Sand bars: constantly
shifting mounds of sand
that form from the
deposition of material from
long shore currents.
A. Barrier Beaches (Islands):
Permanent larger sand bars
that form parallel and
separate from the coast.
Create bays.
IV. Beach Preservation
- Groins, Jetties, sea walls and
breakwaters all protect a coast
from erosion or prevent the
movement of sand along the
beach.
- The side of the
groin with
deposited sand
indicates the
direction of
erosion along the
shore.
Where are
the waves
coming
from?
Closure:
• Obtain a worksheet on Waves. With the
person sitting next to you use the notes to
answer the questions on the handout.
1. Where
is the
longshore
wave
coming
from?
2. Jetties keep sand from
being eroded away from the
beach. They catch the sand
and force the wave to
deposit it nea2 the jetties.
3. Wave erosion creates sea arches and
sea mounts because of differential
weathering by the waves. Wave deposition
creates sand bars and barrier islands due
to deposition of the sand.
Process
Glacier
Wind
Wave
Differences
Similarities