Physical Landform Formations

Question 1

Formation of a v-shaped valley (4 steps)

Answer 1

1. River erodes downwards into the land by hydraulic action
2. Sides of the valley are weakened by weathering e.g. freeze thaw weathering
3. Sides slump into the river under gravity
4. River transports the material away, leaving
   behind a v-shaped valley

Question 2

Formation of a waterfall (5 steps)

Answer 2

1. Hard rock is found on top of soft rock
2. Where the hard rock ends, the soft rock gets eroded by hydraulic action and forms a plunge pool and waterfall
3. Undercutting leaves a ledge of hard rock
4. The ledge collapses under gravity and the position of the waterfall slowly moves up stream
5. Overtime, this leaves behind a steep sided valley in front of the waterfall called a gorge.

Question 3

Formation of a meander (5 steps)

Answer 3

1. Bends in a river are called meanders.
2. Once formed they get more bendy because water is forced to flow faster around the outside bend and slower around the inside.
3. The faster water around the outside causes erosion and makes it deeper here.
4. The outside bend gets undercut and a river cliff forms.
5. On the inside, the slower speed causes the water to deposit and make it shallower here.

Question 4

Formation of an oxbow lake (4 steps)

Answer 4

1. Erosion on the outside bends and deposition on the inside bends make meanders more ‘looped’ over time.
2. Eventually, during a flood the river erodes a new shortcut across the meander neck.
3. Deposition cuts off the old meander loop from the river - forming an oxbow lake
4. Eventually the water in the lake will evaporate or be filled in with and plants and will disappear.

Question 5

Formation of floodplains (4 steps)

Answer 5

1. When a river floods it spreads out onto either side of a river channel.
2. During this stage it deposits fine sand/silt (called ‘alluvium’)
3. This covers any bumps in the landscape making the land flatter - this is the floodplain.
4. When the river overflows, it tends to deposit the larger stones first. These can build up into a natural embankment called levees.

Question 6

Formation of limestone pavements (5 steps)

Answer 6

1. Glaciers/ice sheets scrape away overlying rock and soil - leaving the limestone exposed.
2. Rainwater mixes with carbon dioxide in the air making it slightly acidic. It starts to dissolve the limestone in a process called ‘solution’.
3. Vertical joints in the limestone are enlarged by the rainwater to form ‘grykes’.
4. The rectangular blocks of limestone called clints are separated by the
   grykes.
5. Puddles of rainwater on the clints can dissolve hollows called ‘karren’

Question 7

Formation of stalagmites and stalactites (6 steps)

Answer 7

1. Water mixes with carbon dioxide and produces a weak carbonic acid which can dissolve limestone in a process called ‘solution’.
2. Sometimes drops of this rainwater slowly drops from the roof of a cave
3. There water drips are saturated with calcite. The water evaporates as its waiting to drip down causing the limestone to recrystalise.
4. Slowly, these limestone crystals start to build up causing a limestone ‘icicle’ to start growing down from the ceiling - this is a stalactite.
5. When the drops of saturated water do drip to the floor of the cave, some of the limestone starts to recrystalise here, causing stalagmites to slowly grow upwards.
6. Eventually the stalactite and stalagmite may join together to from a pillar/column.

Question 8

Formation of caves/caverns (4 steps)

Answer 8

1. At the end of the ice age there was a huge amount of melt water coming from the melting ice.
2. Upon reaching limestone, this water would flow underground along the joints and bedding planes of the limestone.
3. This water was slightly acidic, due to mixing with the carbon dioxide in the air and soil so it could dissolve the limestone in a process called ‘solution’.
4. Where there was a high concentration of joints and bedding planes, the water started to dissolve the limestone to form caves.
5. Eventually if the cave continued to grow bigger it would become a cavern.

Question 9

Formation of potholes (4 steps)

Answer 9

1. Potholes are formed in places where limestone is covered by soil or other rocks.
2. Rainwater soaks down through the overlying soil rock and reaches the limestone
3. Here, it starts to dissolve the limestone through a process called chemical weathering
4. Some of the soil above the limestone may slump into the space left by the dissolved limestone creating small dimples in the landscape called shakeholes.
5. Eventually there is nothing left to support the overlying soil/rock and it falls down the gap creating a pothole.

Question 10

Key features of limestone (4)

Answer 10

1. Bedding planes
2. Joints
3. No rivers on limestone
4. Limestone dissolves easily

Question 11

Explain intermittent drainage

Answer 11

Because of the joins and bedding planes, limestone is permeable. So rivers disappear underground when they reach limestone.
The point where the river disappears is called the swallow point and the point where it comes back is called the resurgent stream.

Question 12

How were joins formed?

Answer 12

Pressure release as the limestone was pushed above sea level by plate tectonics.

Question 13

How were bedding planes formed?

Answer 13

Built up of layers of sea creature skeletons on the sea floor.

Question 14

Name 5 upper course landforms

Answer 14

V-shaped valley
Waterfall
River source
Confluences
Tributaries

Question 15

Name 3 middle course landforms

Answer 15

Ox-bow lake
Meander
Eyot

Question 16

Name 3 lower course landforms

Answer 16

Floodplain
Levee
River mouth