Landforms needed for AQA AS-level geography

1. Periglacial Landforms

2. Pingos
Description: They are dome shaped hills that can be
up to 500m in diameter and 50m high. At the core,
there is an ice lens and the surface is made up of
soil and vegetation. The surface may be cracked.
Formation: One way pingos are formed is where
water is trapped in small depression in areas of
impermeable permafrost. Over winter, ground
water beneath lake sediments can be trapped by ice
as the lake freezes. This decrease in temperature
causes this ground water to freeze into an ice lens,
which grows over time. This causes the sediment
above to bulge upwards.

3. Patterned Ground
Description: They can be up to 5m in diameter.
They have uneven ground and bulges surrounded
by rock.
Formation: Ice lenses form due to fluctuating
freezing and thawing in the active layer, forming
uneven ground. Water then migrates to the ice lens.
The lens begins to grow and pushes rocks upwards.
Due to the stones thermal conductivity, cold
patches form beneath them which can push the
stones further upwards. Larger stones roll down the
bulges, forming stone rings.

4. Ice Wedges
Description: These are downward spikes of ice up
to 3m wide and 10m deep.
Formation: In the winter, cracks may form due to
lack of moisture. At first, they may only be a few
mm wide and a metre deep. In the summer, water
may fill this crack which freezes as it reaches the
freezing permafrost. Expanding ice increases the
size of the fracture. After about 100 years, they can
be around 3m wide and 10m deep

5. Nivation Hollows
Description: A localised, isolated patch of snow and
ice that remains through the summer season.
Formation: Snow patches accumulate on a slope
with a north-easterly aspect and doesn’t melt. This
causes physical weathering at the margins. Freeze
thaw action occurs due to fluctuating temperatures,
creating a mass of small rock fragments. This causes
a hollow to occur, which may eventually form a
corrie.