Glaciers2

• Glaciers


  Large rivers (mass) of ice, moving downhill, under the influence of gravity
• Glaciers


  • Open systems with inputs and outputs to external systems, including fluvial and atmospheric systems
  • There are flows of energy, ice, water and sediments between stores
• Inputs to a glacial system


  • Energy (kinetic, thermal)
  • Snow (from precipitation, avalanche or blown-in)
  • Rock debris (from weathering and transportation)
• Outputs from a glacial system

  • Energy (through evaporation and sublimation)
  • Meltwater
  • Water vapour (through sublimation of ice and snow)
  • Icebergs and ice blocks
  • Glacial and fluvio-glacial sediments
• Stores in a glacial system

  • Snow (blown away)
  • Accumulated debris (from weathering, erosional and depositional processes)
  • Ice of the glacier itself
  • Meltwater (stored on and within the glacier)
  • Potential energy (stored from movement of glacier)
• Flows in a glacial system

  • Debris flow (through glaciers from surface storage to landforms)
  • Meltwater flow
  • Glacial movement (through gravity)
• A glacial system has positive and negative feedback loops to keep it in dynamic equilibrium
• Output through ablation (melting) is balanced by glacial input of accumulation (usually snow)
• Equilibrium of the glacier is maintained when input and output are balanced - neither a gain nor loss of ice and the glacier remains the same size
• Characteristics of glaciated landscapes

  • Sharp mountain peaks
  • Steep mountainsides and upper lakes
  • Deep U-shaped valleys or troughs
  • Features of deposition and erosion (striations, outwash plains, braided rivers)
• Glaciated landscapes


  • Can be divided into active (current) or relict (past) landscapes
  • Vary dependent on location (polar, glacial, periglacial and alpine)
  • Geology influences the nature of the landscape
• Igneous rock


  • Harder to erode, often makes up high mountains with steep sides and hollows
  • Large amounts of poorly sorted sand, gravel, and boulders are plucked and pried from the surface and mountains
• Rock flour


  Fine powder created as sediments trapped in ice grind against bedrock, acting as sandpaper to polish the surface
• Glacial striations


  Grooves created as larger rock pieces scrape over the bedrock surface
• Sedimentary and metamorphic rock are found mainly in low-lying areas (already eroded from the uplands) and easier to erode
• Types of glaciers


  • Constrained (valley, piedmont, cirque)
  • Unconstrained (continental glaciers/ice sheets, ice caps, ice shelves)
• Continental glaciers/ice sheets


  Continuous masses of ice, that cover areas greater than 50,000 km³, with no surrounding mountains or features to contain them
• Nunataks

  The tips of mountain peaks showing above a continental glacier/ice sheet
• Ice caps


  Cover areas of less than 50,000km², usually centred on a mountain's high point, with ice flowing in multiple directions to form a cap
• Ice shelves


  Thick, floating slabs of ice, permanently attached to a land mass, where ice flows down to the coast and out onto the ocean's surface
• Piedmont glaciers


  Found at the foot of mountains, where a mass of ice has flowed downslope and fans out, forming lobes of continuous ice
• Valley glaciers


  Ice is surrounded by high mountains and fills the valley, usually ribbon-shaped and varying in length from a few kilometres to over 100km
• Cirque glaciers


  Most common type, confined to either the upper parts of a glacial trough or within the hollowed, cirque basin itself
• Niche glaciers are smaller versions of cirque glaciers
• The glacial landscape is created by the processes of erosion, deposition and flow of material (ice, water and debris) across the Earth's surface
• Flows in a glacial system


  The three main types of flows in a glacial system are debris flow, meltwater flow, and glacial movement.
• Debris flow


  A debris flow is a type of mass movement that involves the movement of a mixture of water, sediment, and rock. In the context of glacial systems, debris flows can occur when meltwater from a glacier mixes with sediment and rock on the glacier's surface, creating a slurry that can flow downhill.
• Meltwater flow


  Meltwater flow refers to the movement of water that has melted from a glacier. Meltwater can flow over the surface of the glacier, or it can flow through the glacier in channels called moulins. Meltwater plays an important role in shaping the landscape around a glacier, as it can carve valleys and transport sediment.
• Glacial movement


  Glacial movement is the slow, creeping motion of a glacier over time. This movement is driven by the force of gravity and is influenced by factors such as the slope of the terrain, the thickness of the ice, and the amount of meltwater present. Glacial movement can lead to the formation of characteristic landforms such as U-shaped valleys, hanging valleys, and cirques.
• Ablation


  The loss of mass from the glacier, e.g. meltwater, avalanches, sublimation, evaporation
• Abrasion


  Small rocks within the base of the glacier rub against the bedrock
• Accumulation


  The addition of mass to the glacier, usually as snow
• Active Layer


  The top layer of soil above permafrost, which thaws annually in summer
• Alpine Regions


  Areas of low temperature in high altitude, mountainous regions
• Arêtes


  A ridge formed between two corries
• Basal Ice Melting


  The weight of a temperate glacier causes meltwater, which will then erode the bedrock through fluvial erosion
• Basal Sliding


  Glaciers sliding over bedrock, due to meltwater between the two surfaces
• Blockfields


  Rock-strewn landscape caused by extensive frost action
• Cold-Based Glacier


  The glacier's temperature remains below zero degrees, so the base of the glacier remains frozen and moves very little
• Compressional Flow


  Ice builds up and thickens due to friction as a glacier travels upwards along a shallow gradient