MASS MOVEMENTS, WIND, & GLACIERS mass movement = when gravity alone causes loose sediments and weathered rock to move downslope sediments and weathered.

MASS MOVEMENTS, WIND, & GLACIERSMASS MOVEMENTS, WIND, & GLACIERS

mass movementmass movement = when gravity alone causes loose = when gravity alone causes loose sediments and weathered rock to move downslopesediments and weathered rock to move downslope1. climate determines which materials and how much is 1. climate determines which materials and how much is available for movementavailable for movement2. all occur on slopes2. all occur on slopes a. most common on slopes greater than 25a. most common on slopes greater than 25oo that have that have annual rainfall of over 90 cmannual rainfall of over 90 cm b. occur more often after heavy b. occur more often after heavy

rainsrains

3. range from very slow motion to sudden slides, fall, & 3. range from very slow motion to sudden slides, fall, & flowsflows

4. factors that affect4. factors that affect a. material’s weighta. material’s weight b. material’s resistance to sliding or flowingb. material’s resistance to sliding or flowing c. trigger that works to shake material loose from slope c. trigger that works to shake material loose from slope such as earthquakes & heavy rainssuch as earthquakes & heavy rains d. amount of water on slope: too much water loosens d. amount of water on slope: too much water loosens sediments as well as makes these heavier & easier to sediments as well as makes these heavier & easier to movemove5. categories:5. categories: a. a. slidesslides = move as block of Earth material = move as block of Earth material b. b. flowsflows = movement involves mixing of particles within = movement involves mixing of particles within

moving massmoving mass c. c. fallsfalls = free fall of Earth material = free fall of Earth material

TYPES:TYPES:RAPID MASS MOVEMENTS:RAPID MASS MOVEMENTS:1. 1. mudflowsmudflows = rapid movement of a large mass of mud and = rapid movement of a large mass of mud and

waterwater a. occur in dry, mountainous areas and sloped, semi-arid a. occur in dry, mountainous areas and sloped, semi-arid regions that have intense, short-lived rainstormsregions that have intense, short-lived rainstorms b. usually after heavy rains, earthquakes, or volcanic b. usually after heavy rains, earthquakes, or volcanic eruptionseruptions c. spreads out in large fan shape at base of slopec. spreads out in large fan shape at base of slope d. d. mud avalanchemud avalanche = fast and = fast and

large mudflowlarge mudflow e. can move down stream e. can move down stream

channels at speeds up to channels at speeds up to 100 km/h100 km/h

2. 2. landslideslandslides = sudden movement of masses of loose rock = sudden movement of masses of loose rock and soil down slope of hill, mountain, or cliffand soil down slope of hill, mountain, or cliff a. generally occur on steep slopesa. generally occur on steep slopes b. often after heavy rainfall, spring thaws, volcanic b. often after heavy rainfall, spring thaws, volcanic eruptions, or earthquakeseruptions, or earthquakes c. relatively thin block of loose soil, rock, and debri c. relatively thin block of loose soil, rock, and debri

separates from underlying bedrockseparates from underlying bedrock d. can carry millions of metric tons of rock and soild. can carry millions of metric tons of rock and soil e. can reach speeds up to 200 km/he. can reach speeds up to 200 km/h f. f. rockslidesrockslides = landslide that occurs = landslide that occurs

when sheet of rock moves when sheet of rock moves downhill on sliding surfacedownhill on sliding surface

3. 3. slumpslump = large block of soil and rock become unstable and = large block of soil and rock become unstable and move downhill move downhill

a. slides along curved slope of surface in one piecea. slides along curved slope of surface in one piece b. occurs in areas that have thick soils on moderate to b. occurs in areas that have thick soils on moderate to steep slopessteep slopes c. often recurs in the same place or adjacent slopesc. often recurs in the same place or adjacent slopes d. trees on blocks are tilted backward so that they seem to d. trees on blocks are tilted backward so that they seem to point more uphillpoint more uphill e. common after rains, can be triggered by earthquakese. common after rains, can be triggered by earthquakes

4. 4. avalanchesavalanches = landslides in mountainous areas with thick = landslides in mountainous areas with thick accumulations of snowaccumulations of snow

a. usually occur on slopes of at least 35a. usually occur on slopes of at least 35oo

b. sun melts surface snow which refreezes at night forming b. sun melts surface snow which refreezes at night forming an icy crust; new snow falls on top eventually building an icy crust; new snow falls on top eventually building heavy enough to slip off & slide down slopeheavy enough to slip off & slide down slope c. ~ 10,000 occur each year in mountains of western US c. ~ 10,000 occur each year in mountains of western US d. can reach speeds up to 300 km/hd. can reach speeds up to 300 km/h

Colorado

5 5 rockfallrockfall = fall of rock from steep cliff = fall of rock from steep cliff a. also called a a. also called a rock avalancherock avalanche b. most rapid kindb. most rapid kind c. rocks range in size from tiny fragments to giant bouldersc. rocks range in size from tiny fragments to giant boulders d. commonly occur in high elevations, steep road cuts, d. commonly occur in high elevations, steep road cuts, rocky shorelinesrocky shorelines e. most often after heavy rains or during earthquakese. most often after heavy rains or during earthquakes f. can form a f. can form a talustalus = cone shaped pile of rock fragments at = cone shaped pile of rock fragments at base of cliffbase of cliff

Canada

Slow Mass Movements:Slow Mass Movements:1. 1. creepcreep = extremely slow, downhill movement of weathered = extremely slow, downhill movement of weathered

rock materialrock material a. most effective typea. most effective type b. water separates and lubricates rock particles allowing b. water separates and lubricates rock particles allowing them to move freely and independently of each otherthem to move freely and independently of each other c. slope does not move as a consolidated massc. slope does not move as a consolidated mass d. can observe in areas where see d. can observe in areas where see

fences or telephone poles tilted fences or telephone poles tilted downhilldownhill

e. movement occurs at a rate of e. movement occurs at a rate of about 1 cm/yrabout 1 cm/yr

2. 2. solifluctionsolifluction = slow downslope flow of waterlogged materials = slow downslope flow of waterlogged materials over frozen or clay rich subsoilover frozen or clay rich subsoil

a. occurs in arctic and mountains areas where subsoil is a. occurs in arctic and mountains areas where subsoil is permanently frozenpermanently frozen b. mudlike liquid produced when water is released from b. mudlike liquid produced when water is released from melting permafrost during warm seasonmelting permafrost during warm season c. in spring and summer top layer thaws and flows downhillc. in spring and summer top layer thaws and flows downhill d. can also occur in warm, humid d. can also occur in warm, humid

areas that have a hard clay areas that have a hard clay layer and ground remains layer and ground remains saturated year-roundsaturated year-round

REDUCING RISKS FOR PEOPLEREDUCING RISKS FOR PEOPLE1. avoid building structures on steep, unstable slopes1. avoid building structures on steep, unstable slopes2. preventive actions2. preventive actions a. dig series of trenches to divert running water around a. dig series of trenches to divert running water around slope and control drainageslope and control drainage b. use steel nets to cover steep slopesb. use steel nets to cover steep slopes c. construct protective fences along highways where c. construct protective fences along highways where rockslides are commonrockslides are common d. build retaining walls at base of d. build retaining walls at base of

weakened slopesweakened slopes3. most only successful in short run3. most only successful in short run

WINDWIND1. erodes dry land more effectively than moist land1. erodes dry land more effectively than moist land2. can transport particles in any direction2. can transport particles in any direction3. normal winds cannot carry particles as those moved by 3. normal winds cannot carry particles as those moved by

moving watermoving water4. primarily occurs in areas with little vegetative cover 4. primarily occurs in areas with little vegetative cover (deserts, seashores, lakeshores, semi-arid areas)(deserts, seashores, lakeshores, semi-arid areas)

WIND EROSION:WIND EROSION:Carries rock particles of various sizesCarries rock particles of various sizes1. 1. sandsand = loose fragments of weathered rocks and minerals = loose fragments of weathered rocks and minerals a. mostly quartza. mostly quartz b. range in diameter from 0.06 to 2 mmb. range in diameter from 0.06 to 2 mm2. 2. dustdust = particles smaller than sand grains = particles smaller than sand grains a. less than 0.06 mm diametera. less than 0.06 mm diameter b. mostly silt and clayb. mostly silt and clay c. usually from soil or volcanic eruption c. usually from soil or volcanic eruption

Particle movementParticle movement1. 1. saltationsaltation = movement of sand by short jumps = movement of sand by short jumps a. occurs when wind speed causes sand grains to roll a. occurs when wind speed causes sand grains to roll along groundalong ground b. move in same direction wind is blowingb. move in same direction wind is blowing2. 2. suspensionsuspension = strong winds cause particles to stay airborne = strong winds cause particles to stay airborne

for long distances for long distances a. dust particles are lifted and carried high into air a. dust particles are lifted and carried high into air and remain in air for several yearsand remain in air for several years b. create large dust storms b. create large dust storms

Methods and Effects:Methods and Effects:1. 1. deflationdeflation = removal of small, loose particles (clay or silt) = removal of small, loose particles (clay or silt)

from ground surfacefrom ground surface a. lowers land surfacea. lowers land surface b. b. desert pavementdesert pavement = surface of closely packed small rocks = surface of closely packed small rocks 1) left after top layer of soil has been removed1) left after top layer of soil has been removed 2) protects underlying land from erosion2) protects underlying land from erosion c. c. deflation hollowdeflation hollow = shallow depression left after layer of = shallow depression left after layer of

exposed soil is erodedexposed soil is eroded 1) form in areas where natural plant cover is gone1) form in areas where natural plant cover is gone 2) common in dry climates2) common in dry climates

2. 2. abrasionabrasion = weathering of rock particles by impact of other = weathering of rock particles by impact of other rock particlesrock particles

a. windblown sand grains strike other sand grains and a. windblown sand grains strike other sand grains and rocks breaking off small fragmentsrocks breaking off small fragments b. some rocks will become pitted and grooved from periodic b. some rocks will become pitted and grooved from periodic wind-blown erosionwind-blown erosion c. c. ventifactsventifacts = rocks shaped by wind-blown sediments = rocks shaped by wind-blown sediments 1) some can be polished smoothed by continued 1) some can be polished smoothed by continued

abrasionabrasion 2) can determine direction of wind by shape2) can determine direction of wind by shape3. large masses of rock erode very slowly and only close to 3. large masses of rock erode very slowly and only close to groundground

Deposits Formed:Deposits Formed:1. 1. dunesdunes = mound or ridge of sand = mound or ridge of sand a. most common type a. most common type b. form where soil is dry and b. form where soil is dry and

unprotected such as deserts unprotected such as deserts and beachesand beaches

cc.. characteristics: characteristics: 1) 1) windward sidewindward side = side facing wind = side facing wind 2) 2) leeward sideleeward side ( (slipface)slipface) = steeper slope, sand is blown = steeper slope, sand is blown

over crest to opposite sideover crest to opposite side 3) shape determine by conditions under which it forms: 3) shape determine by conditions under which it forms:

availability of sand, wind velocity, wind availability of sand, wind velocity, wind direction, direction, amount of vegetation present amount of vegetation present

4) migration occurs when sand blown over crest and 4) migration occurs when sand blown over crest and stops when barrier is reached stops when barrier is reached

5) wind velocity determines height: usually 12 to 25 m 5) wind velocity determines height: usually 12 to 25 m range, some reach 100 m range, some reach 100 m

6) dune vegetation helps to anchor coastal dunes6) dune vegetation helps to anchor coastal dunes

d. types: classification based on shape d. types: classification based on shape 1) 1) barchanbarchan = crescent shaped = crescent shaped

a) most commona) most common b) open side faces away b) open side faces away

from windfrom wind

2) 2) parabolicparabolic = crescent shaped (U-shaped) = crescent shaped (U-shaped) a) open side faces into the winda) open side faces into the wind

3) 3) transversetransverse = series of ridges in long, wavelike patterns = series of ridges in long, wavelike patterns a) form at right angles to wind directiona) form at right angles to wind direction

4) 4) longitudinallongitudinal = form in the shape of a ridge = form in the shape of a ridge a) lie parallel to the direction of winda) lie parallel to the direction of wind

Star dune

2. 2. loessloess = thick deposit of yellowish, fine-grained sediments = thick deposit of yellowish, fine-grained sediments (silt & clay) (silt & clay)

a. accumulation of windblown dusta. accumulation of windblown dust b. soft and easily erodedb. soft and easily eroded c. can form steep bluffsc. can form steep bluffs d. deposits are extremely fertile d. deposits are extremely fertile

for farmingfor farming

3. 3. oasisoasis = fertile green area within a desert = fertile green area within a desert

GLACIERSGLACIERSglaciersglaciers = masses of moving ice that shape landscape by = masses of moving ice that shape landscape by

eroding, transporting, and depositing huge volumes of rocks eroding, transporting, and depositing huge volumes of rocks and sedimentsand sediments

1. formation:1. formation: a. amount of snowfall in winter exceeds amount that melts in a. amount of snowfall in winter exceeds amount that melts in

summersummer b. as snow accumulates pressure increases on bottom of b. as snow accumulates pressure increases on bottom of

snow pile and snow compactssnow pile and snow compacts c. any snow that melts quickly refreezes, forming glacial icec. any snow that melts quickly refreezes, forming glacial ice d. when snow and ice accumulate to a great enough d. when snow and ice accumulate to a great enough

thickness, ice will start move downslope due to gravitythickness, ice will start move downslope due to gravity e. greatest in regions where temperatures are low and snow e. greatest in regions where temperatures are low and snow

fall amounts are highfall amounts are high

2. 2. snowlinesnowline = elevation above which ice and snow remain = elevation above which ice and snow remain year round year round

a. lowest level that permanent snows reach in summera. lowest level that permanent snows reach in summer b. elevation varies from place to placeb. elevation varies from place to place3. 3. snowfieldsnowfield = almost motionless mass of permanent snow = almost motionless mass of permanent snow

and iceand ice a. also called an a. also called an ice fieldice field b. forms by accumulation of snow and ice above the b. forms by accumulation of snow and ice above the snowlinesnowline c. covers land near the poles and tops of some mountains c. covers land near the poles and tops of some mountains at lower latitudesat lower latitudes

4. 4. firnfirn = grainy ice = grainy ice a. formed by partial melting and refreezing which changes a. formed by partial melting and refreezing which changes snow crystals into grains of icesnow crystals into grains of ice b. usually loosely packed, rounded ice grainsb. usually loosely packed, rounded ice grains5. 5. glacial iceglacial ice = mass of interlocking ice crystals = mass of interlocking ice crystals a. pressure of overlying layers become great enough that a. pressure of overlying layers become great enough that ice grains flattenice grains flatten b. air is squeezed outb. air is squeezed out c. pack together so tightly that waterc. pack together so tightly that water

cannot move throughcannot move through d. becomes a bright steel-blue colord. becomes a bright steel-blue color

6. growth depends on:6. growth depends on: a. balance between snowfall received and ice lost by a. balance between snowfall received and ice lost by melting and evaporationmelting and evaporation b. increase or decrease in size may be an indicator in b. increase or decrease in size may be an indicator in annual climatic changeannual climatic change c. when snow is added faster than it melts c. when snow is added faster than it melts →→ increase in increase in sizesize d. when ice disappears faster than snow is added d. when ice disappears faster than snow is added →→ decrease in sizedecrease in size7. weather conditions change 7. weather conditions change

the position:the position: a. warm weather causes it a. warm weather causes it

to melt to melt →→ retreat retreat b. cold weather causes it to b. cold weather causes it to

advanceadvance

TYPES:TYPES:1. 1. valley glaciervalley glacier (alpine glaciers)(alpine glaciers) = long, narrow, wedge-shaped = long, narrow, wedge-shaped

mass of ice mass of ice a. form in high, mountainous areas, exist on every continenta. form in high, mountainous areas, exist on every continent b. must be at high elevations where snow remains year roundb. must be at high elevations where snow remains year round c. usually in hollows or abandoned river valleysc. usually in hollows or abandoned river valleys d. development depends on both temperature and d. development depends on both temperature and

precipitationprecipitation e. flow begins when snow and ice accumulation exceeds 20 m e. flow begins when snow and ice accumulation exceeds 20 m

in thicknessin thickness 1) speed determined by slope of 1) speed determined by slope of

valley floor; temperature and valley floor; temperature and thickness of ice determined by thickness of ice determined by shape of valley wallsshape of valley walls

2) sides and bottom move slower due 2) sides and bottom move slower due to frictionto friction

3) move less than a few mm per day3) move less than a few mm per day

2. 2. continental glacierscontinental glaciers (continental ice sheets)(continental ice sheets) = huge = huge masses of ice and snow found near Earth’s polar regionsmasses of ice and snow found near Earth’s polar regions a. covers an area of 50,000 square km or morea. covers an area of 50,000 square km or more b. covers 10% of Earth’s surfaceb. covers 10% of Earth’s surface c. thickest in center causing it to spread outward in all c. thickest in center causing it to spread outward in all directions under its own weightdirections under its own weight d. can be currently found in Greenland, Antarctica, and d. can be currently found in Greenland, Antarctica, and northern Canadanorthern Canada

MOVEMENT:MOVEMENT:1. often called “rivers of ice”1. often called “rivers of ice”2. on average moves about 100 m per year2. on average moves about 100 m per year

- some move more (km) and some move less (few cm)- some move more (km) and some move less (few cm)3. 3. surgesurge = sudden movement that occurs after long periods of = sudden movement that occurs after long periods of

little movementlittle movement4. 4. basal slipbasal slip = meltwater acts as a lubricant moving entire = meltwater acts as a lubricant moving entire

mass along bedrock mass along bedrock a. moves by slipping at its basea. moves by slipping at its base b. able to work over small b. able to work over small

barriers in path by melting barriers in path by melting and refreezingand refreezing

5. 5. internal plastic flowinternal plastic flow = solid ice crystals slip over each other = solid ice crystals slip over each other causing a slow forward motion causing a slow forward motion

a. pressure of overlying layers cause layers of ice to slide a. pressure of overlying layers cause layers of ice to slide over each otherover each other b. determine rate of motion by slope and by the thickness b. determine rate of motion by slope and by the thickness and temperature of iceand temperature of ice 1) faster nearer to surface than near the base1) faster nearer to surface than near the base 2) friction with rock surface slows the flow rate2) friction with rock surface slows the flow rate6. center moves faster than sides (especially valley glaciers)6. center moves faster than sides (especially valley glaciers)

FEATURES:FEATURES:1. 1. crevassescrevasses = large, deep cracks in surface = large, deep cracks in surface a. can be more than 30 m deepa. can be more than 30 m deep b. usually covered by thin layer of snowb. usually covered by thin layer of snow c. break open under the slightest weightc. break open under the slightest weight2. 2. ice shelvesice shelves = ice sheet moves out over the ocean = ice sheet moves out over the ocean a. Ross Ice Shelf is largesta. Ross Ice Shelf is largest b. rise and fall of tides break off large pieces of leading edgeb. rise and fall of tides break off large pieces of leading edge3. 3. icebergsicebergs = large blocks of ice that drift into the ocean = large blocks of ice that drift into the ocean a. most of its mass (size) is below surface of watera. most of its mass (size) is below surface of water b. size variesb. size varies c. hazardous to shipsc. hazardous to ships

EROSION BY:EROSION BY:1. 1. pluckingplucking = meltwater freezes and erodes rock by loosening = meltwater freezes and erodes rock by loosening

particles, then lifting and carrying them particles, then lifting and carrying them downslopedownslope

2. 2. abradingabrading = scouring of bedrock surface by rock fragments = scouring of bedrock surface by rock fragments over which ice movesover which ice moves

a. a. striationsstriations = parallel grooves and scratches formed from = parallel grooves and scratches formed from embedded rocksembedded rocks

b. b. glacial groovesglacial grooves = very large striations = very large striations c. c. glacial polishglacial polish = silt and sand embedded in glacier base = silt and sand embedded in glacier base

produces a smooth, shiny finish produces a smooth, shiny finish d. d. rock flourrock flour = abrasion grinds rocks and other coarse = abrasion grinds rocks and other coarse

particles into silt size sediment particles into silt size sediment e. scratches and grooves run parallel to direction of glacial e. scratches and grooves run parallel to direction of glacial movementmovement which can show direction of ice movementwhich can show direction of ice movement

LANDFORMS CREATED:LANDFORMS CREATED:1. U-shaped valleys1. U-shaped valleys2. 2. cirquecirque = steep walled semicircular depression = steep walled semicircular depression a. eroded into a mountain peak a. eroded into a mountain peak b. one side open to a valleyb. one side open to a valley3. 3. aretearete = sharp, narrow ridges; form where two cirques on = sharp, narrow ridges; form where two cirques on

opposite sides of a valley meet opposite sides of a valley meet4. 4. hornhorn = sharp, pyramid shaped peak = sharp, pyramid shaped peak a. rock summit eroded by glaciers a. rock summit eroded by glaciers b. usually where 3 or more cirques intersect near the b. usually where 3 or more cirques intersect near the summitsummit5. 5. tarntarn = small lake that = small lake that

forms inside a cirqueforms inside a cirque

6. 6. roches moutonneesroches moutonnees = rounded knob of rock = rounded knob of rock a. smooth, gently sloping sidea. smooth, gently sloping side b. faces direction from which glacier cameb. faces direction from which glacier came7. 7. hanging valleyshanging valleys = tributary glacial valley whose mouth lies = tributary glacial valley whose mouth lies

high above floor of main valleyhigh above floor of main valley a. form from small tributary glaciers that meet main valley a. form from small tributary glaciers that meet main valley glacierglacier b. may see waterfalls form where these join b. may see waterfalls form where these join 8. ice sheets erode by leveling landforms, producing fairly 8. ice sheets erode by leveling landforms, producing fairly smooth, rounded landscapessmooth, rounded landscapes

DEPOSITION:DEPOSITION:1. 1. erraticserratics = large boulders = large boulders a. transported to present location by a glaciera. transported to present location by a glacier b. composition usually differs from that of bedrock over b. composition usually differs from that of bedrock over

which it now lieswhich it now lies2. 2. glacial driftglacial drift = all sediment deposited by a glacier or its = all sediment deposited by a glacier or its

meltwaters meltwaters a. a. glacial tillglacial till = mixed debri carried embedded in ice and on = mixed debri carried embedded in ice and on

tops, sides, and front edges tops, sides, and front edges 1) sediments scraped off by base of glacier1) sediments scraped off by base of glacier 2) left behind when glacial ice melts2) left behind when glacial ice melts b. b. stratified driftstratified drift = sediment sorted, deposited, and layered = sediment sorted, deposited, and layered

by glacial meltwaterby glacial meltwater c. c. meltwatermeltwater = water that results from melting of glacial snow = water that results from melting of glacial snow

and ice and ice 1) usually milky in color1) usually milky in color 2) presence of fine rock particles2) presence of fine rock particles

3. till deposits:3. till deposits: a. a. morainesmoraines = ridges of unsorted rock material on the ground = ridges of unsorted rock material on the ground

or on glacier or on glacier 1) 1) lateral morainelateral moraine = deposited along sides of valley glacier = deposited along sides of valley glacier

as long ridgeas long ridge 2) 2) medial morainemedial moraine = adjacent lateral moraines join = adjacent lateral moraines join

togethertogether- form dark stripes on glacier surface- form dark stripes on glacier surface

3) 3) ground moraineground moraine = unsorted material left beneath = unsorted material left beneath glacier when ice meltsglacier when ice melts

4) 4) drumlinsdrumlins = long, tear-shaped mounds of till = long, tear-shaped mounds of till a) often found in clustersa) often found in clusters b) parallel to direction of glacial movementb) parallel to direction of glacial movement c) forms when glacier flows over and reshapesc) forms when glacier flows over and reshapes

5) 5) terminal moraineterminal moraine = deposits at the snout or front of a melting = deposits at the snout or front of a melting glacier glacier

a) belts of small ridges of tilla) belts of small ridges of till b) many depression contain lakes or pondsb) many depression contain lakes or ponds

4. stratified drift deposits:4. stratified drift deposits: a. a. outwashoutwash = deposit left by streams flowing from a melting = deposit left by streams flowing from a melting

glacier glacier b. b. outwash plainoutwash plain = deposit which lies in front of terminal = deposit which lies in front of terminal

moraine moraine 1) sediment spreads out into larger valley or plain1) sediment spreads out into larger valley or plain 2) crossed by many meltwater streams2) crossed by many meltwater streams c. c. kettleskettles = depressions across the outwash plain = depressions across the outwash plain 1) created by melting a large chunk of glacial ice left 1) created by melting a large chunk of glacial ice left

buried in the drift buried in the drift 2) when ice melts will form lakes or ponds = 2) when ice melts will form lakes or ponds = kettle lakeskettle lakes d. d. eskerseskers = long, winding ridges of gravel and coarse sand = long, winding ridges of gravel and coarse sand 1) form when fill meltwater 1) form when fill meltwater

tunnelstunnels 2) deposited by streams flowing 2) deposited by streams flowing

under melting glacier under melting glacier e. e. kameskames = small mounds of = small mounds of

sand and gravelsand and gravel

ice ageice age = long period of climatic cooling during which = long period of climatic cooling during which continental ice sheets cover large areas of earth’s surfacecontinental ice sheets cover large areas of earth’s surface1. time of extensive glacial activity1. time of extensive glacial activity2. earliest one = 600 mya2. earliest one = 600 mya3. most recent one began 2 - 3 million years ago, retreated 3. most recent one began 2 - 3 million years ago, retreated about 18,000 years agoabout 18,000 years ago4. climate changes4. climate changes a. drop in average temperature of about 5a. drop in average temperature of about 5ooCC b. have increase in snowfallb. have increase in snowfall5. 5. glacial periodglacial period = time when ice sheets advance (during cold = time when ice sheets advance (during cold

periods) periods) a. during last period covered nearly 1/3 of land surfacea. during last period covered nearly 1/3 of land surface b. sea level was 140 m lower than todayb. sea level was 140 m lower than today6. 6. interglacial periodsinterglacial periods = time of warmer temperature and ice = time of warmer temperature and ice

sheets retreatsheets retreat

7. causes:7. causes: a. a. Milankovitch theoryMilankovitch theory = small, regular changes in earth’s = small, regular changes in earth’s orbit and in the tilt of earth’s axis cause ice agesorbit and in the tilt of earth’s axis cause ice ages b. three types of periodic changes occur as earth moves b. three types of periodic changes occur as earth moves around sunaround sun 1) change in shape of earth’s orbit1) change in shape of earth’s orbit 2) change in tilt of earth’s axis2) change in tilt of earth’s axis 3) change in circular motion (3) change in circular motion (precessionprecession) of earth’s axis) of earth’s axis c. these will change the c. these will change the

amount of solar energy amount of solar energy reaching earth’s surfacereaching earth’s surface