the illustrated history of glacial erosion l.
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The Illustrated History of GLACIAL EROSION. This is a glacier. Actually it’s several glaciers coming together to form a larger one. The glaciers are hundreds of feet thick. They have enormous mass. They flow downhill due to the FORCE OF GRAVITY . These are VALLEY or ALPINE

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Presentation Transcript
slide2

This is a glacier. Actually

it’s several glaciers coming

together to form a larger one.

The glaciers are hundreds of

feet thick. They have enormous

mass. They flow downhill due

to the FORCE OF GRAVITY.

These are VALLEY or ALPINE

glaciers. They flow in valleys

between mountains. They are

small when compared with

CONTINENTAL glaciers which

cover entire continents.

Antarctica is covered by a

continental ice sheet.

The dark bands in the glacier are rocks

ripped from the sides of the mountains as

the glaciers flow. The dark bands are called

MORAINES. The rock will be carried to the

point where the glacier melts and then it will

be deposited.

A glacier is a rock conveyor belt.

slide3

Here’s another view of a glacier showing the Terminal Moraine. It forms

at the point at which the rate of melting is equal to the flow of ice. You

can also see a Medial Moraine in the middle of the glacier.

slide5

The V-shaped valley seen to the

right is typical of stream or water

erosion. As the stream flows, it’s

‘cutting tools’ which are the rocks

and stones it carries, cut deeper

and deeper into the streambed

forming a V-shape.

If the climate gets colder and the

valley fills with ice the glacier will

rip rocks from the sides as well as

the bottom of the valley. This will

widen the valley and change it’s

shape.

To the left is a wide

U-shaped valley which

is typical of glacial

erosion.

V-shaped = streams

U-shaped = glaciers

slide6

Another view of a typical

U-shaped glacial valley.

And another...........................

slide7

The power of glaciers can be seen in this photo of 'El Capitan' aka Half Dome

mountain in Yosemite Valley in California. As glaciers moved through this

valley they sliced this solid granite mountain in two and scooped out the

U-shaped valley to the left.

slide8

As glaciers flow, the rocks embedded

in the ice cut deep PARALLEL GROOVES

in the bedrock beneath. When the glaciers

melt these parallel grooves remain as

evidence that the glaciers were there.

The picture to the right shows bedrock

exposed at the Bronx Zoo.

Above more parallel grooves and

scratches in exposed bedrock.

slide9

Sometimes the grooves are

very deep and dramatic such as these from the Peruvian

Andes (left).........

or these (right) known as Kelley’s

Grooves found on Kelley’s Island,

Ohio.

slide10

These rocks were embedded in the ice

at the bottom of a glacier. As the glacier

moved over bedrock it was rocks like

these that cut the parallel grooves. In

the process these rocks tumbled and

rolled becoming SCRATCHED and

POLISHED.

SCRATCHED and POLISHED

boulders are evidence of glacial

erosion.

slide11

Unlike streams or rivers

glaciers can carry enormous

blocks of stone for many,

miles. When the glaciers

melt these rock are left

stranded far from their

origins.

Such rocks are called

ERRATICS. An erratic is a

boulder that was transported

to its present location and is

generally unrelated to the

underlying bedrock.

The ERRATIC on the left was deposited

in Central Park.

slide12

Some erratics come to rest

in strange places.

Some are deposited closer to home

like this boulder in Eastport.

slide13

This is a satellite view

of the Finger Lakes

region of New York State.

The finger lakes are very

deep and narrow parallel

lakes scooped out during

the last ices age.

The glaciers movement

from north to south

accounts for the

N-S orientation of these

bodies of water.

Lakes like these are found

all over the world wherever

the last continental ice

sheet scraped and

scarred the land.

slide14

If the U-shaped depression

carved by the glaciers

reaches all the way to the sea it is often referred to as a ‘fjord’. A fjord is a long, narrow salt water bay carved by glaciers and they are found in many countries all over the world.

The photo was taken at Misty Fjords in Alaska.

slide15

The material transported by a glacier is

called TILL. When the glacier melts the

till is deposited in a pile. There is no

sorting as occurs when a stream slows.

UNSORTED SEDIMENTS is good evidence

of glacial deposition.

Above and to the right are

pictures of unsorted glacial

till. Material from fine silt to

large boulders are mixed

together randomly.

You live on unsorted glacial

till since Long Island is composed completely of glacial material.

slide16

Sometimes the glacial till is deposited in mounds or hills. These are called DRUMLINS. The drumlins above are found in Scotland but similar features are found all over the northern hemisphere. Often drumlins are so large that they cannot be appreciated for what they are except when photographed from high altitudes.

slide18

As glaciers retreat (melt) huge blocks of ice may remain buried in the earth. As these blocks gradually melt they leave deep depressions which fill in with water forming "KETTLE LAKES" such as those seen above. Kettle lakes represent more evidence that a region has undergone glaciation.

slide19

A summary of glacial features

1) U-shaped valleys

2) Parallel grooves in bedrock

3) Scratched and polished boulders

4) Erratics

5) Long, deep, glacial lakes

6) Unsorted sediments

7) Drumlins

8) Kettle lakes

Learn these terms. Whenever you see one on a test or

on the regents the answer is always "GLACIERS".

slide20

Glaciers are an endangered species. This is the Muir glacier in Glacier Bay, Alaska photographed in 2007.

slide21

The Muir Glacier is retreating rapidly. Ice is melting faster

than new ice can replace it. The arrows show where the

glacier was just a few years ago. As it melts it exposes

rock that appears lighter because it hasn’t had time to

weather.

slide22

These views show how the Muir Glacier has changed in just over half a century. In that time it has retreated over 20 km and it continues to get smaller every year.

People may debate the causes of global warming but the evidence is clear. The Earth IS warming.

slide23

This is the Mendenhall Glacier in Juno, Alaska. The picture was taken in 2007. If these people had been standing here in 1987 they would have been under 65 feet of ice.

slide24

Lastly, a very quick review of essential terms that are

likely to appear on the regents..............

What kind of sediments do glaciers produce?

UNSORTED

What kind of valleys are associated with glaciers?

U-SHAPED

What term applies to a boulder deposited by a glacier?

ERRATIC

What do glaciers do to the rocks they pass over?

They cut LONG,PARALLEL GROOVES

What evidence indicates that a rock was transported by

a glacier?

It may be SCRATCHED and POLISHED