2.7. Landforms of deposition

Question 1

What are swash aligned beaches?
(bay)

Answer 1

• tend to form in low energy environments
• affected by waves arriving roughly parallel to the shore
• beach is sand or shingle
• high energy waves transport sand, leaving behind coarse shingle
• low energy waves deposit sand or mud

Question 2

What are drift aligned beaches?

Answer 2

• high energy environments
• waves approach the coast at an angle
• longshore drift moves sediment along beach, often culminating in formation of a spit
• sediment may be graded
• finer shingle particles are likely to be carried further by longshore drift and also increased rounding

Question 3

Where are larger pebbles usually found on a beach and why?

Answer 3

• at the top of a beach
• constructive waves carry a range of sediment sizes but the weak backwash only drags back smaller pebbles

Question 4

Why do pebbles at the bottom of the beach tend to be more rounded?

Answer 4

It’s due to constant action= abrasion and attrition

Question 5

What do seasonal changes do to a beach?

Answer 5

• sediment is dragged offshore by destructive waves in winter and returned by constructive waves in summer
• beach profiles are steeper in summer, more constructive waves
• in winter, more destructive waves so strong backwash so sediment dragged off beach

Question 6

What are barrier beaches?
(bar)

Answer 6

• formed as an extension to a spit
• longshore drift moves sediment along the coastline until there’s a change in the coastline, a spit develops in a bay and once the spit develops across the whole bay, a barrier beach forms
• colonisation by vegetation (roots) can stabilise the barrier beach and trap further sediment, keeping the barrier beach above sea even at high tide
• if the barrier beach is disconnected from the mainland, it forms a barrier island

Question 7

What is a tombolo?

Answer 7

A spit that connects an island to the mainland

Question 8

What is an offshore bar?

Answer 8

• submerged ridges of sand or coarse sediment created by waves offshore from the coast
• destructive waves erode sand from the beach with their strong backwash and deposit it offshore
• act as sediment sinks and sediment input stores
• can absorb wave energy

Question 9

What is an estuary?

Answer 9

• when the river meets the sea, the difference in densities between salt and freshwater cause a chemical reaction called flocculation
• the clay particles stick together, making them heavier
• this means they sink to the bottom creating an estuary mudflat

Question 10

What is a salt marsh?

Answer 10

• Tend to develop in sheltered estuaries behind spits. As the spit develops, the area behind it becomes sheltered.
• Silt is deposited by the river which gradually builds up to form a mudflat. The mud flat continues to build to build and rise above sea level with the addition of further silt.
• Vegetation which is highly adapted to the environment colonises the mud which itself traps further sediment.
• The salt marsh environment is colonised by halophytic vegetation which decomposes and adds organic matter to the soil.
• Over time, a wilder variety of plants will be able to survive in the salt marsh.