Transcript Glaciers
Earth Science Notes Glaciers What is a glacier? • Glaciers are a large mass of ice formed on land by the compaction of snow and creep down slopes due to the stress of its own weight. Glaciers survive from year to year. Glaciers are major cause of erosion in Northern Climates and higher elevations. What are the controlling forces that create glaciers? Amount of precipitation • Glaciers can only form where the accumulation of snow remains throughout the year. • This happens only when annual snowfall exceeds losses from evaporation or melting. What are the controlling forces that create glaciers? Temperature of air mass are also important • Rockies may get 40 feet of snow in winter, but all melts in summer. • Antarctica receives 6": snow annually, yet its ice sheet is extending into seas. What effects do glaciers have on the land? Glaciers are a major force of erosion. • Plucking – the action of glaciers picking up loose rocks and placing them somewhere else. Glaciers are a major force of erosion. Glacial erosion causes • Aretes • Cirques • Horns • Striations Glaciers are a major force of erosion. Arêtes • Arêtes – Sharp ridges formed by two or more cirques cutting into the same mountain. Cirques • Cirques – Bowl-shaped depressions where glaciers cut into mountain walls. Horns • Horns – sharp, triangular peaks created when many glaciers erode a mountain. Striations • Striations – shallow parallel scars on rock produced by glaciers Glaciers and Topography Glacier Deposits • Glaciers deposit a lot on sediments leaving divers land formations Glacier Deposits • Glacial deposition – boulders and rocks left over from glaciers transporting them. • Till – a pile of debris deposited by a glacier, consisting of a mixture of various materials. Glacier Deposits Moraines – A glacial feature formed from accumulation. • Terminal Moraine – an accumulation at the outermost edge where a glacier existed. • Ground Moraine – Gently rolling hills and plains deposited by ice. Glacier Deposits • Lateral Moraine – Ridges of till on the sides of a glacier • Medial moraine - is formed down the middle of a glacial valley, where two glaciers have joined. – The lateral moraine from each glacier merges at the point where the glaciers join. Glacier Deposits • Depositions by ice sheets - when ice sheets deposit material they can form many different kinds of features. Glacier Deposits • Drumlins – glacial deposits formed when the glacier is carrying to much sediment. Glacial Deposits • Erratic - large boulder left in places beyond the glacier Glacial Deposits • Eskers – glacial deposits formed when sediments are deposited in ice tunnels or by streams on top of the ice (See fig. 12 p. 217) Glaciers Summary • What is a glacier • Forces creating glaciers • Glaciers effect on land (topography) – Landforms created by erosion – Landforms created by deposition