Ice on the Land

Ice on the Land

1. Ice forms

   • Glacier
   • Ice sheet
   • Ice cap

2. Ice Ages

3. How glaciers move

4. Glacial processes

   • Erosion
     • Transportation
     • Plucking
       • Abrasion
     • Freeze-thaw Weathering

5. Glacial landforms

   • Erosional
     • Depositional
       • Drumlins
         • Mounds of till and boulder clay with their long axis parallel to the direction of the glacier's motion. -they can be up to 50m tall, 800m long and 500m wide. -they can occur in groups called swarms.
         • The ice usually becomes overloaded with sediment
           • Drumlins are formed when the glacier is advancing but melting (ablation zone)
             • The deposition of the boulder clay and till is triggered when the glacier comes past a small obstacle e.g. a small rock outcrop
               • Most of the boulder clay and till is deposited on the 'upstream' end of the rock, making that end blunt and steep sided
                 • The glacier shapes the 'downstream' end to be tapered
       • Moraines
         • Lateral
           • A ridge of till found along the sides of a glacier
           • Medial
             • A ridge of till in the middle of a glacier (where two ice streams meet)
             • Recessional
               • A hill of till and boulder clay between the glacier's snout and the terminal moraine. It represents a stationary phase in the glacier's retreat.
               • Terminal
                 • A hill of till and boulder clay found where the ice's furthest extent was. It is usually curved
                 • The glacier pushes material to the ablation zone.
                   • The glacier melts and this material is deposited as a hill at the ice's furthest extent
               • The glacier becomes stationary or retreating and the material is deposited.
             • Two smaller glaciers merge
               • 2 of the lateral moraines from the 2 smaller glaciers merge in the middle of the new glacier.
           • Material is detached from the valley sides using freeze-thaw weathering
             • This material lands on the sides of the glacier and is transported by the glacier.
               • The glacier melts and this material is deposited at the glacier sides as a ridge of till.
         • Glaciers flow plastically so bulldoze material.
           • They transport (push) this to the ablation zone where it is deposited on melting
             • When the glacier melts, material transported supraglacially (obtained from freeze-thaw weathering).
       • Boulder clay/ till
         • a poorly sorted mixture of mud, sand and gravel-sized material deposited directly from glacier ice).
         • It is unstratified, unsorted (unlike rivers) and individual stones tend to be angular and sharp. This is because most material just land on top of the glacier and with it - attritition never erodes and smoothens it. However, subglacial debris may be smoothened as it grinds along the rock underneath in abrasion.
           • Transported as debris and deposited when the glacier melted.
     • Arête
       • A sharp, knife-edged ridge found on a mountainside often between two corries.
       • Corrie
         • An armchair-shaped hollow in the mountainside.
         • Pyramidal peak
           • A steep sided, pyramid-shaped peak.
           • The backward erosion of 3+ glaciers
         • Snow collects in a mountainside hollow
           • Over time, as more and more snow builds up the snow is compressed into ice so that a glacier forms
             • Abrasion is the process where rock material frozen into the glacier erodes the rock below and it causes the corrie's overdeepening. It also helps to form the rock lip.
               • Plucking is the process by which rock freezes onto the base of the mountain, and it then pulls away pieces of rick from there. Plucking steepens the corrie's backwall.
                 • Over time these processes continue and once the glacier has melted, we are left with an armchair-shaped hollow in the mountainside. Sometimes a tarn is left behind.
       • Snow collects in mountainside hollows
         • The snow builds up and compresses to form ice (ie. a glacier) on either side of the mountain
           • Plucking causes the steepening of the backwall of each glacier.
             • Abrasion couses corrie over-deepening
               • The processes continue and the corrie moves downwards and inwards
                 • This leaves a sharp, narrow ridge inbetween with steep corrie backwalls
     • Glacial trough/ U-shaped valley
       • Ribbon lake
       • Glaciers flow plastically so can't flow around interlocking spurs
         • So they bulldoze through them. This is possible as glaciers have enough energy behind them to do so
           • So they trunkate the interlocking spurs
             • Abrasion widens and deepens the valley

6. Case Studies

   • The Alps
   • Gangotri Glacier
   • Kashmir, India
     • The French Alps
   • The Alps

7. Glacial retreat

8. Avalanches

9. Climate Change

10. Distribution of cold environments