Periglacial processes

• What is Frost Heave?

  Expansion of ice crystals under stones in the soil pushes the stones up to the surface
• What landform does Frost Heave form?

  Stone Polygons
• What are Stone Polygons?

  As stones burst through the surface during Frost Heave, heavier stones roll outwards and small stones stay in the centre, forming shapes in the landscape
• What is Ice Contraction?

  Refreezing of the active layer causes soil to contract, and the cracks fill up with meltwater
• What landforms are formed by ice contraction?

  Ice wedges and Pingos
• What are Ice Wedges?

  Meltwater in cracks of the soil freeze and widen, they can grow up as much as 1m thick and 3m deep
• What are Pingos?

  A very large dome-shaped isolated hill on flat plains, with summits that rupture to expose their ice cores
• How large can Pingos be?

  They can have diameters up to 500m and heights of 50m
• How are pingos formed?

  Surface water infiltrates the ground and freezes, the ice expands and the process repeats until the sediment is pushed up to form hills
• What is Frost Shattering also known as?

  Freeze Thaw Weathering
• What are some landforms associated with Frost Shattering?

  Block fields, Scree and Tors
• What is a Block Field?

  Flat mountains covered with large angular boulders that have broken away due to frost shattering
• What is Scree?

  Mixture of angular and unsorted rock deposits at the foot of steep slopes. They are also called talus cones
• What is a Tor?

  Well jointed rocks that usually stand above block fields, made of resistant rock that hasn’t been eroded by frost shattering
• What is Nivation?

  Névé in north facing hollows collects and enlarges the hollow via abrasion
• What does Wind and Meltwater Rivers do to erode?

  Absence of vegetation allows wind action and water to erode landscapes
• What is a Solifluction Lobe?

  The active layer in summer begins to slide down the hill (solifluction), and collects at the bottom (the lobe)
• What is Loesś?

  Equivalent of a large sand dune, where strong winds collect fine sediment into large dunes
• What is a catena?

  A connected series of related features changing down a slope due to periglacial processes