EES 1030 1st Edition Lecture 18 Intro to Earth ScienceDistribution of earth’s water:Earth’s hydrosphere consists of 3.26 million cubic miles of water. Approximately 84% of Earths freshwater is stored in Glaciers.Glacier: thick mass of ice that originates on land-Part of earth’s hydrological cycle and rock cycle. Covers 10% of Earths land surface.Valley glacier: glacier confined to flow down a mountain valley typically a former stream valley from an accumulation center at its head.Ice sheet: very large thick ice mass of glacial ice flowing outward in all directions from 1 or more accumulation centers often called continental ice sheets, exists on a large scale Antarctic ice sheet:Contains 80% of earth’s ice and 66% of earth’s fresh water. It would cover 150% of the United States. If melted it would raise the sea level 60-70 meters.Formation of Glaciers:Glaciers form in areas where more snow is added then melts or evaporates 3 parts:1) Zone of accumulation 2) Snow line3) Zone of Wastage How it forms:1) Snowflakes become smaller, thicker, and more spherical (granules) 2) Air is forced out of pore spaces 3) Snowflakes recrystallized into denser masses of small grains called Firn4) Under pressure firn fuzzes into a large mass*Glaciers are always moving to flow downslope b/c of gravitational pull*Basil slope: Movement within ice when under pressure ice behaves as a plastic materialPlastic flow: occurs where ice is unfracturedZone of fracture: upper brittle part of glacier where tension causes crevasses to form in brittle areas Crevasses: big deep cracksSurge: extremely rapid movements can move up to meters per dayCalving: wastage of glaciers where large piles of ice break off making ice burgs in the waterZone of wastage: area lost due to meltingSnowline: lower limit of snow accumulation- Advance: accumulation exceeds loss- Retreat: loss exceeds accumulation- Balance: loss and accumulation are equalRole of melt water:Forms are refreezes b/c of pressure variations at the base of the glacierRefreezing: water traps sediments and debris with in the icePlucking: lifting of rock by iceGlacial polish: polished bedrock surface Glacial striations: groves made in the bedrock by glaciersRock Flour: finely pulverized rockGlacial trough: U-shaped valley made by alpine glacierHanging valley: tributary that enters a glacial troughLakes: form where lower areas in glacial landscapes are filled with water and precipitationFiords: steep sided inlet of the sea formed when a glacial trough was partially submerged.Glacial Drift: refers to all sediments of glacial originTill: material deposited directly by iceStratified drift: sediments deposited by glacial melt water typically well-sorted and stratifiedTillite: rock formed by glacial tillVarres: rock formed when stratified drift is lithifiedErratics: ice transported things such as bouldersTerminal moraine: stony debris deposited by melt at the leading edge of a glacier Drumlin: smooth elongated barrel hills formed by tillEsker: sinuous ridged stratified drift deposited by a stream flowing in a tunnel beneath a