2A glacier is a rock conveyor belt. This is a glacier. Actuallyit’s several glaciers comingtogether to form a larger one.The glaciers are hundreds offeet thick. They have enormousmass. They flow downhill dueto the FORCE OF GRAVITY.These are VALLEY or ALPINEglaciers. They flow in valleysbetween mountains. They aresmall when compared withCONTINENTAL glaciers whichcover entire continents.Antarctica is covered by acontinental ice sheet.The dark bands in the glacier are rocksripped from the sides of the mountains asthe glaciers flow. The dark bands are calledMORAINES. The rock will be carried to thepoint where the glacier melts and then it willbe deposited.A glacier is a rock conveyor belt.
3Here’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. Youcan also see a Medial Moraine in the middle of the glacier.
5The V-shaped valley seen to the right is typical of stream or watererosion. As the stream flows, it’s‘cutting tools’ which are the rocksand stones it carries, cut deeperand deeper into the streambedforming a V-shape.If the climate gets colder and thevalley fills with ice the glacier willrip rocks from the sides as well asthe bottom of the valley. This willwiden the valley and change it’sshape.To the left is a wideU-shaped valley whichis typical of glacialerosion.V-shaped = streamsU-shaped = glaciers
6Another view of a typical U-shaped glacial valley.And another
7The 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 thisvalley they sliced this solid granite mountain in two and scooped out theU-shaped valley to the left.
8As glaciers flow, the rocks embedded in the ice cut deep PARALLEL GROOVESin the bedrock beneath. When the glaciersmelt these parallel grooves remain asevidence that the glaciers were there.The picture to the right shows bedrockexposed at the Bronx Zoo.Above more parallel grooves andscratches in exposed bedrock.
9Sometimes the grooves are very deep and dramatic such as these from the PeruvianAndes (left)or these (right) known as Kelley’sGrooves found on Kelley’s Island,Ohio.
10These rocks were embedded in the ice at the bottom of a glacier. As the glaciermoved over bedrock it was rocks likethese that cut the parallel grooves. Inthe process these rocks tumbled androlled becoming SCRATCHED andPOLISHED.SCRATCHED and POLISHEDboulders are evidence of glacialerosion.
11Unlike streams or rivers glaciers can carry enormousblocks of stone for many,miles. When the glaciersmelt these rock are leftstranded far from theirorigins.Such rocks are calledERRATICS. An erratic is aboulder that was transportedto its present location and isgenerally unrelated to theunderlying bedrock.The ERRATIC on the left was depositedin Central Park.
12Some erratics come to rest in strange places.Some are deposited closer to homelike this boulder in Eastport.
13This is a satellite view of the Finger Lakesregion of New York State.The finger lakes are verydeep and narrow parallellakes scooped out duringthe last ices age.The glaciers movementfrom north to southaccounts for theN-S orientation of thesebodies of water.Lakes like these are foundall over the world whereverthe last continental icesheet scraped andscarred the land.
14If the U-shaped depression carved by the glaciersreaches 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.
15The material transported by a glacier is called TILL. When the glacier melts thetill is deposited in a pile.There is no sorting as occurs when a streamslows.UNSORTED SEDIMENT is good evidenceof glacial deposition.Above and to the right arepictures of unsorted glacialtill. Material from fine silt tolarge boulders are mixedtogether randomly.Long Island is composed completely of glacial material.
16Sometimes the glacial till is deposited in mounds or hills 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.
18As 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.
19A summary of glacial features 1) U-shaped valleys2) Parallel grooves in bedrock3) Scratched and polished boulders4) Erratics5) Long, deep, glacial lakes6) Unsorted sediments7) Drumlins8) Kettle lakes
20Glaciers are an endangered species Glaciers are an endangered species. This is the Muir glacier in Glacier Bay, Alaska photographed in 2007.
21The Muir Glacier is retreating rapidly. Ice is melting faster than new ice can replace it. The arrows show where theglacier was just a few years ago. As it melts it exposesrock that appears lighter because it hasn’t had time toweather.
22These 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.
23This is the Mendenhall Glacier in Juno, Alaska This is the Mendenhall Glacier in Juno, Alaska. The picture was taken in If these people had been standing here in 1987 they would have been under 65 feet of ice.
24Lastly, a very quick review of essential terms What kind of sediments do glaciers produce?UNSORTEDWhat kind of valleys are associated with glaciers?U-SHAPEDWhat term applies to a boulder deposited by a glacier?ERRATICWhat do glaciers do to the rocks they pass over?They cut LONG,PARALLEL GROOVESWhat evidence indicates that a rock was transported bya glacier?It may be SCRATCHED and POLISHED