GLACIER
A. Large mass ice accumulates over 100-1000s yearsB. Form from the accumalation of snow1.Snow compacted and recrystallized to form glacial iceC. Most glaciers move slowlyD. Glaciers erode, transport, deposit large amounts of materiaE.Glacial action is responisible for shaping landformsF. Glaciers cover approx. 10 percent of Earths surface today
Types of Glaciers
A. VALLEY GLACIERS1. Form in mountanious areas move down stream valleys2. all continents except AustraliaB.ICE SHEETS (continental glaciers)1. Glaciers move outward in all directions from one or more centers of accumalation2. found only in Antartica (thickness -14000 feet) and Greenland
Glacial Movements
A. ZONE OF FRACTURE- Upper150 feet of glacierB. ZONE OF FLOW1. Glacier movement occurs2.Basal Slip-glacier moves along underlying bedrock due to lubrication by meltwater3. Plastic flow-ice actually flows in this zone
Glacial Budget
A.ZONE OF ACCUMULATION1. Snow accumulation and ice formation occur here2. Ice is added to the glacierB. ZONE OF WASTAGE1. All the snow from the previous winter and glacial ice are losta. meltingb. Calving-pieces of glacier break off when glacier flows into a lake of oceanC. GLACIAL BUDGET1. Terminus-end of valley glacier of an ice sheet2. When accumulation>wastage, terminous advances3.When wastage>accumulation, the terminus retreats4. When accumulation=wastage, terminus remains stationary
Glacial Erosion
A. Plucking-pieces of bedrock freeze to bottom of glacier and pulled out as the glacier movesB. Abrasion-1. Abrasive effect of particles transported along bottom and sides of glacier2. Glacial striations- scratches made on underlying bedrock long particles moved along bottom glacier3.Rock Flouri. Pulverized rock material (silt and clay sized) created rocks grind against each other during transportii. May be picked up by wind and deposited as loess
EROSIONAL FEATURES CREATED BY VALLEY GLACIERS
A. U-shaped glaccial trough- valley glaciers widden, deepen, straighten stream valleysB. Cirques-bowl-shaped depressionas at head of glacial valleyC. Hanging valley-1.Smaller tributary glaciers cant erode their valleys as deeply as main glacier2. When glaciers melt, smaller valleys are left above main main valley3.Waterfalls from where water flows from hanging valleysD.Aretes-knifelike ridges separate glacial valleys or cirquesE. Horns- pyramidlike peaks form in areas where three or more ciques surround peakF. Fjords-drowned glacial valley along coasts.
GLACIAL DEPOSITION
A.DRIFT- general term for sediment deposited by glaciers1. Till- poorly sorted glacial material deposited when glacial ice melts2. Stratified drift-glacial deposits trans and depo by meltwaterB.MORAINES1. Layers of till2.Lateral moraine- material trans along sides of valley by valley glacier, forms lateral moraine when deposited3. Medial Moraine-formed where two lateral moraines join in a valley glacier4. End of Morainesa. Form at terminus of a valley glacier or ice sheetb.Terminal end moraine- form when terminus of a glacier is stationaryc. Ground Moraine-layer of till deposited as glacier retreatsd. Recessional moraine- form when the terminus of a retreating glacier becomes stationaryC. VALLEY TRAINS AND OUTWASH PLAINS1.Outwash plains-stratified drift deposited in front of ice sheet2. Valley trains-stratififed drift deposited beyond terminus of valley glaciers
Ice sheets
A.OFTEN PRODUCE ROLLING TOPOGRAPHYB. FEATURES ASSOCIATED WITH RETREATING ICE SHEETS1. Drumlinea. symmetrical hills composed of tillb. Probably molded in the zone of flow2. Eskers- sinuous ridges of stratified drift deposited by meltwater flowing under the edge of glaciers3. Kettles-depressions formed when a block of ice is left being by a retreating glacier and buried in drift4.Braided streamsa. Meltwater flowing frm glaciers carries large load of sedimentb. Gravel and sand bars are deposited in the channelsc.When water level is low, water has to flow around the bars producing a network of channels.5. Terminal end and recessional moraines
Pleistocene Epoch
A. Pleistocene Epoch1. 1.6 my -10,000 years2.Ice sheets covered approximately 30 percent of Earths surface3. Evidence for four glacial advances and retreats on land4. Evidence from ocean floor sediment indicates at least 20 warming/cooling cycles occuredB. EFFECTS OF GLACIATION1. Sea level changesa. Occur when glaciers advance and retreatb. Sea level was about 450 feet lower than today at times during Pleistocene2.Isostatic rebounda. Crust was depressed by weight of ice sheetsb. When ice sheets retreated, crust slowly reboundedi. Some areas are still rebounding from Pleistocene glaciation3.Some mammals grew to unusually large sizesa. Mammoths, ground sloths, Irish elk, glyptodonts, etc.4.Pluvial Lakesa. Climates during the Pleistocene were cooler and wetterb. Permanent lakes formed in areas such as Death Valleyc. Great Salk Lake is a remnant of much larger lake that formed during Pleistocene