Landforms and their Evolution

The landforms carved and built by running water, groundwater, glaciers, waves and wind, and the stages of a river landscape.

Key ideas

Youth: few streams, shallow V-shaped valleys, waterfalls and rapids; maturity: deep V-valleys and wider floodplains; old age: meanders, levees and ox-bow lakes near sea level.
Running water carves gorges, canyons, potholes and plunge pools, and builds alluvial fans, deltas, floodplains, natural levees and point bars.
Groundwater in limestone makes karst: sinkholes, uvalas, lapies and caves with stalactites and stalagmites.
Glaciers carve cirques, horns and U-shaped valleys, and leave moraines, eskers, drumlins and outwash plains.
High rocky coasts have cliffs, wave-cut platforms and stacks; low sedimentary coasts have beaches, bars, spits and lagoons.
Wind in deserts makes pediments, pediplains, playas, mushroom rocks and dunes such as barchans and seifs.

Remember

River gradient	fall in metres ÷ length in km = m per km (steeper suggests youth)
Glacier or cliff movement	metres = cm per day (or year) × days (or years) ÷ 100
Gorge or canyon?	gorge: near-vertical sides, same width top and bottom; canyon: step-like sides, wider at the top
Stalactite or stalagmite?	stalactites hang from the roof; stalagmites rise from the floor
Moraines	terminal at the toe, lateral along the sides, medial in the centre, ground as a sheet of till
Barchan	crescent dune with wings pointing downwind

Watch out

Mixing up stalactites and stalagmites.
Calling a spit, delta or moraine erosional: they are deposits.
Forgetting to divide by 100 when turning cm into metres.

Worked example

Suppose a valley glacier moves 50 cm a day. (a) How many metres does it move in 260 days? (b) How many cm in a week? (c) Name two depositional landforms the glacier leaves when it melts.

Working: 50 × 260 ÷ 100; 50 × 7

Answer: (a) 130 m (b) 350 cm (c) moraines and eskers (also drumlins and outwash plains)