Presentation on theme: "Glaciers By Dylan & Tony. Overview Describe how Glaciers form. Show Types of glaciers. explain how glaciers Move. Something about snow. Snowline Snowfield."— Presentation transcript:
Glaciers By Dylan & Tony
Overview Describe how Glaciers form. Show Types of glaciers. explain how glaciers Move. Something about snow. Snowline Snowfield Valley glacier Continental ice sheets Basal slip Internal Plastic Flow Features of glaciers Erratic Till deposits Stratified drift deposition Yellow snow
Formation of glaciers Snowline- The elevation at which snow falls and doesnt melt throughout the year. Snowfield (ice field)- is the accumulation of snow above the snowline. Firn- a type of ice that is frozen, partially melted and then refrozen ect.. It was originally snow but do to all the freezing and melting has transformed into ice crystals In deep regions of snow deposits, the firns are compressed to the point where all the oxygen is pressed out of them and thus they turn blue, the white color returns after that area is exposed to more oxygen for instance if a portion of it were to fracture. The rate at witch a glacier would grow or shrink is proportional to the rate of snow that is melted and/or evaporated. More snow, less melting= growth… less snow more melting= decrees in size.
Types of glaciers Valley glacier- when ice moves down a valley, the larger the surrounding mountains the larger the glacier (usually) Continental ice sheets- its a giant sheet of ice, it can occur over oceans. The only two places currently hosting these phenomena are Greenland and Antarctica. Ice sheets can be extremely thick, for instance in some regains of Antarctica the ice sheet is over four thousand meters thick Scientists hypothesize that if these two sheets were to melt, the sea level would raise by over 60 meters.
Movement of glaciers It is said that some glaciers travel one hundred meters per year, but that is all dependent upon the conditions of the amount of snow fall vs the melting. There are two type of glacial movement Basal slip and internal plastic flow
Basal slip Over time the weight of all the ice on top will cause the ice in contact with the group to melt and then the water freezes and the above ice slips over it.
Internal Plastic Flow This process is where the ice firns just tumble over each other on the bottom layer of ice. Rate of movement is determined by the angle of the slope
Features of glaciers Do to all the different stresses a giant mount of moving ice makes, deep cracks can form and they are called crevasses Some times they arent visible other times they are.
Glacial erosion Cirque- when a glacier pulls rocks form the floor of the upper valley Arêtes- are jagged ridges that form between the cirques Horn- when several arêtes join up to form a kind of jagged pyramid
Glacial deposition Erratic- when a bolder is transported by a glacier Glacial drift -till is made up of jumbled rock material -Stratified drift is where rock material has been sorted and deposited
Till deposits Landorms built from till are called moraines. Lateral moraine- where sediment is deposited on the side of a valley glacier, usually along a ridge. Medial moraine- is when two or more valley glaciers meet and there lateral moraines combine Ground moraine- any material not picked up by the glacier.
Stratified drift deposition Out wash plain- small rock fragments that are some times carried when parts of a glacier melt Kettles are formed when glacial ice are is buried in a drift when the drift collapses the indention is still there, they some times form lakes Eskers- what the material from the water forms, they can form things that look like raised winding roads.
lakes The great lakes were formed by glaciers Also most salt lakes were formed by glaciers as well, they initially were not very salty but as time went on and more evaporation occurred, the saltier they got.