Transcript Slide 1

GLACIERS
CHAPTER 5
HONORS EARTH SCIENCE
What is a glacier?
a thick mass of moving ice
http://www.jadecoast.ca/Sawyer%20glacier.JPG
How do glaciers form?
Step 1: Snow accumulates.
More snow falls during the
winter than melts in the
summer.
Trans Labrador Highway
Step 2: Snow changes to firn.
As snow accumulates,
its weight compress
the individual
snowflakes to form
firn.
FIRN
http://www.gsw.edu/~bcarter/physgeol/glac/firn.jpg
Firn
http://crevassezone.org/Photos/Graphics/3441L-(Firn).jpg
Step 3: Firn is compressed to form solid glacial ice.
http://patti.tensegrity.net/album/alaska/thompson/ice4.jpg
http://www.asf.alaska.edu:2222/img/firn_diagram.gif
http://207.239.98.44/IcelandI%20232.jpg
Step 4: The ice begins to move.
Plastic flow- weight of
glacier moves out like
pancake batter
http://www-math.science.unitn.it/Bike/Countries/Europe/Tour_Reports/Tour_of_the_Alps/Gallery/glacier.jpg
When the climate cooled…
Ice advanced over the land, moving southward from Canada over
the Great Lakes Region.
Glaciar Perito Moreno, in Santa Cruz province, Argentina. It hasn’t happened since 1988
and it is said to be one of the most extraordinary natural events in the world.
- Roberto Cerrudo
Glacier terms
• Zone of Ablation- melting
• Zone of Accumulation- snow accumulates
• Crevasse- cracks
• Advance- more accumulation than melting
• Retreat- more melting than accumulation
VALLEY GLACIER
How do glaciers erode the surface?
• Plucking –
freeze/thaw process
lifts particles into ice
Striations- parallel
scratches made from
rocks in ice scraping
against bedrock
Glaciers pick up lots of sediment as
they advance over the land.
http://www.geographyjim.org/Newzealandglacier.jpg
TYPES OF GLACIERS
• Alpine (Valley)Glaciers
– glaciers that form at
high elevation in
mountain valleys
• Ice sheets or
Continental Glaciers
form in polar regions such
as Greenland and
Antarctica.
http://daac.gsfc.nasa.gov/DAAC_DOCS/geomorphology/G
EO_9/geo_images_9/Fig9.20.gif
Cirque
• A bowl-shaped
depression located
where a glacier
begins to form
http://crevassezone.org/Photos/Graphics/4163L-(Cirque).jpg
Horn
Kinnerly Peak - Glacier National Park
• A tall, pointed rock
peak left at the top of
a mountain
http://www2.nature.nps.gov/geology//parks/glac/car0348.jpg
The most famous horn in the Alps…
The Matterhorn
• Located on the
boundary between
Switzerland and Italy,
the Matterhorn’s
summit is 4478 m
above sea level.
Arete – spines or ridges of rock that
separate glacial valleys
U-shaped Valley - Yosemite National Park
V-shaped valleys become U-shaped valleys
as glaciers move through them…
Step 1
Step 3
A typical river
valley
Glacier fills valley,
widening and
straightening the
channel
Step 2
Step 4
Over time,
running water
cuts a deeper
V-shape.
Glaciers melt leaving
a U-shaped valley
Hanging Valley
• a small valley
that has not
eroded as deep
as the main
valley that it is
connected to
• Waterfalls often
form at hanging
valleys.
TYPES OF GLACIAL DRIFT
(Sediments)
• TILL- unsorted; deposited by ice
• STRATIFIED DRIFT- layered; deposited
by meltwater streams
• OUTWASH- sorted sand; deposited by
meltwater
Erratics
•Boulders carried great
distance by the glacier
•Don’t match
surrounding rock
Erratics along Lake Michigan Shoreline
TYPES OF GLACIERS
• Alpine (Valley)Glaciers
– glaciers that form at
high elevation in
mountain valleys
• Ice sheets or
Continental Glaciers
form in polar regions such
as Greenland and
Antarctica.
MORAINES
• Deposited along edge
of glacier during
melting
• Terminal- very end of
glacier
• Lateral- side of glacier
• Recessionalprogresses behind
terminal
MORAINES
http://www.helsinki.fi/~jhyvonen/PB/M/Cerro%20Tronador%20moraine-pp.JPG
• MADE OF TILL- unsorted sediment
terminal moraine – unsorted sediments
deposited at the edge of the melting glacier
Ground Moraine- flat till deposits
between recessional moraines
Kettle Lakes
• Made from ice
blocks
Kettle Lakes
• Kettle lakes form when blocks of ice break off the front edge
of a glacier, become buried by sediment. The ice melts
leaving a hole which fills with water creating a lake.
Drumlins
• Hills of sediment
deposited by the
glacier- till
ESKERS
• Winding ridges of
stratified drift
• Deposited by
meltwater streams
• Mined for gravel
KAMES
Cone shaped deposits
Deposited at end of meltwater streams
Stratified drift
Why do scientists believe that
glaciers once covered Michigan?
Moraine Deposits = unsorted sediments
Moraines are made of
unsorted sediments.
Only mass movements
and glaciers deposit
unsorted sediments.
Since there are no
large hills or
mountains in Michigan
for this sediment to fall
down, it must have
been deposited by the
glaciers.
Moraine Deposits have the same shape as the
Great Lakes.
• Michigan
moraines run
parallel to the
shoreline.
• The same
process that
formed the
moraines formed
the Great Lakes.
Each of the Great Lakes began as a river.
Image from Earth Science, Tarbuck and Lutgens, 2003
As the climate cooled…
• The rivers froze.
• Glaciers moved
through them –
widening and
deepening them to
form today’s lake
bottoms.
• The sediment
removed from the
river valleys was
deposited in the
moraines covering
our state. This is
why the moraines
run parallel to the
shorelines of the
Great Lakes.
When the climate began to warm,
the glaciers began to melt and retreat.
http://www.msstate.edu/dept/geosciences/CT/TIG/WEBSITES/LOCAL/Spring2002/Michael_Marsicek/images/Great_Lakes_Formation.gif
The fresh water from the melting glaciers filled in the
deep U-shaped valleys that they had carved and
turned them into the lakes we have today.
http://www.ofps.ucar.edu/gapp/networks/images/greatlakes_map.jpg
What other evidence do we have that
glaciers once covered our state?
• Depositional features such as drumlins and
kettle lakes.
Kalkaska, Michigan
Kettle Lakes
Why do scientists believe that
glaciers once covered Michigan?
• Michigan is covered with unsorted moraine
deposits.
• The moraine deposits follow the outline of
Great Lakes..
• Erratics
• striations
http://homepage.tinet.ie/~jconsidi/BWS/karst4.jpg
Kelly’s Island, Ohio
Kelly’s Island
Glacial grooves
Granite Island, Lake Superior
MI
Calumet, MI
N47°14’77’’ W88°26’82’’
Resources
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http://cse.cosm.sc.edu/erth_sci/Erosion/plucking.jpg
http://www.skidmore.edu/academics/geo/courses/ge101/Pictures/Glaciers/GlacialSt
riations.jpg
http://www.go2moon.com/image/Valdez-Glacier.jpg
http://www.glaciers.pdx.edu/kennicott/photos99/glacier.jpg
http://www.brownbearsw.com/photos/pws/moraine.jpg
http://www.homepage.montana.edu/~geol445/hyperglac/depproc1/moraine.JPG
http://www.ucalgary.ca/~dgsmit/MORAINE.jpg
http://mac01.eps.pitt.edu/harbbook/c_viii/images/icefields/Hwb0530.GIF
http://www.geographyhigh.connectfree.co.uk/s3glacgeoghigh34b.gif
http://www.uwsp.edu/geo/faculty/lemke/images/lithosphere/drumlin_diagram_small.
gif
http://online.sd43.bc.ca/della/images/drumlin.jpg
http://www.geology.wisc.edu/~qlab/g420/drumlin.jpg
http://www.bbc.co.uk/scotland/education/bitesize/standard/img/geography/glaciatio
n/g98.gif
http://pbisotopes.ess.sunysb.edu/esp/Science_Walks/carmans/kettle-hole.gif
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http://perth.uwlax.edu/faculty/stoelting/Intro/Guides/Images3/southern_Kettl
e_Moraine_lakes_WI_800.jpg
http://images3.vrbo.com/vrbo/images/18982c.jpg
http://www.on.ec.gc.ca/greatlakeskids/images/g_lakes_form.gif
http://wrgis.wr.usgs.gov/docs/parks/glacier/UvalleyB.gif
http://wrgis.wr.usgs.gov/docs/parks/glacier/UvalleyC.gif
http://www.jchl.co.uk/photos/greenland/Valley.jpg
http://www.emporia.edu/earthsci/student/martel1/ice.jpg
http://wrgis.wr.usgs.gov/docs/parks/glacier/gifJPGdisplay.html
http://www.uwsp.edu/geo/faculty/lemke/alpine_glacial_glossary/images/mor
e_examples/canada_cirque01_dh.jpg
http://www.uoregon.edu/~millerm/Kluane1.jpeg
http://people.surfaceeffect.com/pete/photos/folksholiday/yosemitevalley/vall
ey2.jpg
http://www.theotherpages.org/images/image200.jpg
http://www.northforkmedia.com/spiveyscience/images/glacialerosion/pages/
grinnellcirqueareteetc_jpg.htm
http://www3.uakron.edu/modlang/97trip/d16f.jpg
http://tvl1.geo.uc.edu/ice/Image/icland/Greenland.html
http://www.bougerolle.net/photos/matterhorn.jpg
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http://perth.uwlax.edu/faculty/stoelting/Intro/Guides/Images3/glacial_erratics
_Lake_Michigan_WI_800.jpg
http://www.fettes.com/Cairngorms/images/Easter_Island.jpg
http://rt23.com/Scenery/spring/images/tripod_rock.jpg
http://ic.ucsc.edu/~rocks/eart109/Photo_Composition/Top_Pothole.jpg
http://perth.uwlax.edu/faculty/stoelting/Intro/Guides/Images3/southern_Kettl
e_Moraine_lakes_WI_800.jpg