Cold Environments: Ice Movement

Cold Environments: Ice Movement

1. Types of Ice Movement

   • Basal Sliding: Movement of large block of ice - usually in a series of short jerks. Occurs when meltwater helps to lubricate the base of the ice. Meltwater forms on the upslope side of obstacles on the valley floor. Additional resistance causes and increase in pressure, which leads to localised melting of ice-called pressure melting.
   • Internal Deformation: Involves ice crystals slipping and sliding over each other. Ice crystals may become deformed or fractured, and gradually move downhill in response to gravity. Occurs in both warm and cold glaciers, often the same time as basal sliding.
   • Cold Glaciers are glaciers that are so cold that they are stuck permanently to the bedrock
   • Warm Glaciers are glaciers that are in warmer climates, so there is meltwater

2. Variations in the Rate of Ice Flow

   • Extensional Flow is when there is a sudden increase in gradient, the ice will flow faster and may become thinner as it is stretched. This stretching can sometimes result in cracking to form crevasses.
   • Compressional Flow is when there is a sudden decrease in gradient and will slow the ice flow. All the ice becomes compressed, closing the gaps of the crevasses that the extensional flow made
   • Between these two types of flow, the ice moves in a curved or rotational manner, otherwise known as Rotational Flow. This helps corries to form.
   • Fastest flow is towards the centre. This is because the friction exerted by the valley sides slows down the movement at the edges of the ice.