Ignaz VenetzSwiss engineerPresented a paper about St John’s bayLouis aggasizSon of a ministerNaturalistsZoologistGeologistSet out to disprove ignaz venetz’s theoryMilutin milankovitchSiberian astrophysicistSuggested three astronomical eventsEccentricity (change in shape of the earth’s orbit)Variations in the earths orbital eccentricity- the shape of the orbit around the sun. 100000 yards.Changes in oliquity0 changes in the angle that earths axis makes with te plane of earths orbitPrecession- the change in the direction of the earths axis of rotation, the axis of rotation behaves like the spin axisWhat is snow?Snow forms from the condensation of water vapor that is at a temperature below freezing. This is called sublimation, the process by which material in the gaseous state passes directly to the solid state without first becoming liquidAll snow has hexagonal symmetry which reflects the internal arrangement of hydrogen and oxygen atomsStages for the formation of snow crystalsSnowGranular iceFirmGlacial iceWhat is a glacierA mass of ice formed by the recrystallization of snow, that has flowed under the influence of gravity100 ft of snow compresses into 10 ft of icezone of accumulationmore material is added by new deposition annually than is lost by meltingzone of ablation or meltingmore material is lost by melting and evaporation than is deposited by snowequilibrium lineupper and lower zones of an alpine glacierglaciers move in two waysglacial creep(plastic flow)- moves downhill by the force of gravity. Fastest flow is at top middle. As glaciers move over bumps, deformation causes crevasses to form in the rigid zone.Glacial sliding(basal slip)- heat is generated at bottom of glacier due to friction and ground heat. Plastic zone of glacier is also more fluid due to enormous pressure, similar to plastic rock at depth. This type of flow is most erosive to rock below.Rates of glacial movementImperceptible 8-76 mm per 1000 years in the sub polar regionVariegated glacier in Alaska surges at regular intervals about once every 17-20 yearsGlaciers erode rocks in two waysPlucking (quarrying) bedrock is pulled out by ice. Produces a rock knob or roche moutonnee.Abrasion- rocks and debris moved within the glacier cause erosionTwo primary controls on the formations of glaciersElevation and latitudeGlaciers TWO MAJOR TYPESAlpine- (also called valley glaciers and mountain glaciers) occur in highland areas and flow down slopeContinental(also called ice sheets) occur at high latitudes and during ice ages at lower latitudesFormation of alpine glaciersSnow line- line above which snow remains all yearAbove the snow line snow accumulates, thickens, and changes form to a granular compact form called FIRN.As the snow/firn is buried deeper it is compressed and recrysttallised into the deep blue form called blue iceHanging valleySmaller glaciers erode less material so after glaciers retreat upon climate change, hanging valleys and waterfalls appear on the sides of the main valleyA cirque is where the glacier initially formsThree or more intersecting glaciers on a mountain leaves behind a hornRidges between glaciers are called arêtesA col is formed when the rock separating two adjacent cirques erodes, eventually resulting in an ice field.Types of morainesTerminal moraines- furthest extent of glacial advanceRecessional moraines- left behind as glaciers retreatMoraines that may be seenEvidence of ice age glaciation95 of north America is covered by ice sheet deposits. This glacial material is generally referred to as glacial drift, till and moraineglacial drift- unsorted till +stratified driftREST OF SLIDE IS ON PHONEErratics- a rock that has been plucked and moved by a glacierDesertification- distritbution of deserts48 million square mile1/3 of the land surface is deserttwo climatic typesdesert which is aridsteppe which is semi aridweatheringphysical weathering is dominatechemical weathering is limitedephemeral streams (influent)braided channels commonflash floods can kill you and dramatically rework the landscape, most of the erosional workusually land locked, interior drainages, few tributariesclimate controlled large land masseGeol exam 3 notes 04/04/2014Ignaz Venetz- Swiss engineer- Presented a paper about St John’s bayLouis aggasiz- Son of a minister- Naturalists- Zoologist- Geologist- Set out to disprove ignaz venetz’s theoryMilutin milankovitch- Siberian astrophysicist- Suggested three astronomical events- Eccentricity (change in shape of the earth’s orbit)o Variations in the earths orbital eccentricity- the shape of the orbit around the sun. 100000 yards. o Changes in oliquity0 changes in the angle that earths axis makes with te plane of earths orbito Precession- the change in the direction of the earths axis of rotation, the axis of rotation behaves like the spin axisoo What is snow?- Snow forms from the condensation of water vapor that is at a temperature below freezing. This is called sublimation, the process by which material in the gaseous state passes directly to the solid state without first becoming liquid- All snow has hexagonal symmetry which reflects the internal arrangement of hydrogen and oxygen atomsStages for the formation of snow crystals- Snow- Granular ice- Firm- Glacial iceWhat is a glacier- A mass of ice formed by the recrystallization of snow, that has flowed under the influence of gravity- 100 ft of snow compresses into 10 ft of icezone of accumulation- more material is added by new deposition annually than is lost by meltingzone of ablation or melting- more material is lost by melting and evaporation than is deposited by snowequilibrium line- upper and lower zones of an alpine glacierglaciers move in two ways- glacial creep(plastic flow)- moves downhill by the force of gravity. Fastest flow is at top middle. As glaciers move over bumps, deformation causes crevasses to form in the rigid zone.- Glacial sliding(basal slip)- heat is generated at bottom of glacier dueto friction and ground heat. Plastic zone of glacier is also more fluid due to enormous pressure, similar to plastic rock at depth. This typeof flow is most erosive to rock below.Rates of glacial movement - Imperceptible 8-76 mm per 1000 years in the sub polar region- Variegated glacier in Alaska surges at regular intervals about once every 17-20 yearsGlaciers erode rocks in two ways- Plucking (quarrying) bedrock is pulled out by ice. Produces a rock knob or roche moutonnee.- Abrasion- rocks and debris