mock only - Distinctive Landscapes

What is deposition

• The dropping of materials onto land when the water does not have enough energy to carry it

• Heavier sediments drop first

 

How are headlands and bays formed

• Headlands and bays form at discordant coastlines

• Hard rock erodes slowly, forming headlands

• Soft rock erodes quickly, forming bays

 

How is a cave formed

• Crack in the rock is opened up by hydraulic action and abrasion

• The crack grows into a cave by hydraulic action

How is an arch formed

• When water breaks through the headland it forms an arch

 

How is a stack formed

• When the arch erodes more, chemical weathering causes it to collapse and form a stack

• Further weathering and erosion leaves a stump

 

Example of stack/stump?

Old Harry Rocks, Dorset

How is a beach formed

• Strong swash pushes beach sediment up the beach at an angle, in the same direction of the waves

• Then the weaker backwash brings some materials straight

• This continues along the shore and the sediment forms a beach

 

How is a spit formed

• Longshore drift moves the material along a coastline

• When the coastline changes direction, the material is deposited

• The deposited material builds up, formed a long ridge called a spit

Which landforms have been created by geomorphic processes on the Jurassic Coast

• Lulworth Cove

• Old Harry Rocks

 

Lulworth Cove

• A concordant coastline has the same type of rock along its length

• The alternating bands of hard and soft rock run parallel to the coast

• Lulworth Cove is situated on the south coast of England on a concordant coastline

• The entrance to the cove is narrow where the waves have cut through weaknesses in the limestone

• Then the cove widens where the softer clays have been more easily eroded

• At the back of the cove is a band of more resistant chalk so erosion is slower here

Old Harry Rocks

• Old Harry is two miles northeast of Swanage

• Old Harry lies at the eastern edge of the Isle of Purbeck

• The headland is part of Ballard Down

• The chalk formations are commonly called the Old Harry Rocks and the name Old Harry refers to the single stack of chalk furthest out

• There was another stack as well until 1896 but it tumbled out to sea due to erosion and is now a stump

 

How does geology influence geomorphic processes on the Jurassic Coast

• The Jurassic coast is made of bands of resistant (chalk and limestone) and non resistant (clay) rock

• There are both concordant and discordant coastlines, resulting in a wide range of landforms

• Softer rock is easily eroded by hydraulic action

• Harder chalk and limestone are weathered and eroded more slowly, so stand out as headlands

Which climate factors influence geomorphic processes on the Jurassic Coast

• Temperature

• Wind

• Rainfall

 

How does temperature influence geomorphic processes on the Jurassic Coast

• The Jurassic Coast has warm dry summers and mild wet winters

  • Therefore freeze-thaw weathering is rare

• Salt weathering occurs on coasts as the evaporation of sea water causes salt crystals to build up

 

How does wind influence geomorphic processes on the Jurassic Coast

• South West prevailing winds can bring storms from the Atlantic

• High energy destructive waves increase erosion through hydraulic action, eroding cliff bases

  • Unstable cliffs means mass movement may occur

 

How does rainfall influence geomorphic processes on the Jurassic Coast

• There is relatively low annual rainfall

• Heavy rainfall during winter storms saturates soil, causing slumping of cliffs

Human activity on the Jurassic Coast

• Limestone, a valuable building material, is quarried on the Isle of Portland

  • Quarries expose areas of rock and cause chemical erosion

• Coastal footpaths are also eroded by tourists and vegetation is trampled

  • This exposes underlying soil and rock to weathering

 

Impact of climate change

• A warmer atmosphere makes intense storms more likely, creating larger and more powerful waves

  • This will increase rate of erosion

• Additionally, more intense rainfall leads to greater weathering of cliffs

  • Leading to mass movement of rocks, causing more landslides

What coastal management does the Jurassic Coast have

• Groynes

• Beach nourishment

• Sea wall

 

Groynes on the Jurassic Coast

• In Swanage, groynes have been in place since the 1800s

• There are currently 18 timber groynes

Pros and cons of groynes

• 👍 - Builds a beach, encouraging tourism

• 👎 - Trapping sediment starves beach further down the coastline

 

Beach nourishment on the Jurassic Coast

• In 2005, 90km³ of sand was deposited onto the beach

• This project took 1 year and cost £2.2 million

• Every 20 years, the beach in Swanage needs to be replenished with 40km³ of sand

Pros and cons of beach nourishment

• 👍 - blends in with existing beach, makes it more appealing for tourists

• 👎 - needs to be replaced often, expensive

 

Sea wall on the Jurassic Coast

• There is a 1.8km sea wall in Swanage

• It has not changed since the 1920s

Pros and cons of sea wall

• 👍 - protects base of cliff, protects against coastal flooding, forms a promenade for tourists

• 👎 - costs 2k / metre, doesn't fully stop erosion as waves can bounce of the wall and erode the beach instead

 

How successful were coastal management strategies

• Tourism has increased 20% since the implementation of coastal management strategies according to the RGS

• Flooding has been prevented over the past 30 years thanks to the sea wall

6 marker - explain the formation of one landform in your case study area

Name: Old Harry Rocks

• Old Harry Rock is found on a chalk headlands

• Headlands are vulnerable to high energy waves

• These widen gaps in the cave via hydraulic action and abrasion

• The cave breaks into an arch through hydraulic action and abrasion

• Chemical weathering weakens the top of the arch

• Gravity then makes it collapse, creating the stack that is old harry

What are the three types of weathering

• mechanical

• chemical

• biological

What is mechanical weathering

• Freeze thaw

• Water seeps into cracks in rocks

• When water freezes, it expands, wedging the rock apart

• With repeated freeze thaw cycles, rock breaks off

What is chemical weathering

• Rain naturally acidic, causing chemical weathering in rocks

 

What is biological weathering

• Mix of physical and chemical

• More example when roots extend (physical) and leaves decompose (chemical)

 

What are the two types of mass movement

• Sliding

• Slumping

What is sliding

• Sudden movement of rock and soil along a zone of saturated soil

 

What is slumping

• Movement of permeable rock and soil that is lying on top of impermeable material

• Due to heavy saturation

What are the four types of erosion

• Abrasion

• Hydraulic action

• Attrition

• Solution

What is abrasion

• When waves pick up rocks and smash them against the coast

 

What is hydraulic action

• When water enters cracks in the cliff

• Causing the crack to expand

What is attrition

• When rocks hit each other, becoming smaller and rounder

What is solution

• When rocks slowly dissolve in the water

 

What are the four types of transport

• Traction

• Saltation

• Suspension

• Solution

What is traction

• When boulders roll along the sea bed

 

What is saltation

• When pebbles bounce along the sea bed

 

What is solution

• When particles dissolve in water

 

What is suspension

• When particles float and are carried along