3.b Submergent coastal landscapes form as sea level rises. Flashcards
What are the 3 submergent landforms?
Rias, fjords, and shingle beaches.
When were rias formed?
During the Flandrian Transgression.
What is a ria?
Submerged river valleys.
What are the low areas of a ria like?
The lowest part of the river’s course, and the floodplains alongside the river, may be completely drowned.
What are the high areas of a ria like?
The higher land, forming the tops of the valley sides and the middle and upper part of the river’s course, remains exposed.
What are rias underlain with?
They are underlain by alluvial deposits.
What is the cross-section and centre of a ria like?
Its cross-section is shallow
The centre is deeper.
What are rias influenced by?
They are influenced by tides (inter-tidal).
Submerged at high tides, sandbanks are exposed at low tides.
What is the structure of a ria like?
V-shaped, with gently sloping sides.
Give an example of a ria?
Salcombe and Padstow in Cornwall.
When were fjords formed?
During the Flandrian Transgression.
What is a fjord?
Submerged glacial valleys.
What is the structure of a fjord like?
They have steep, almost cliff-like, valley sides.
U-shaped, harsh dropping sides.
What is the water like in a fjord?
Water is uniformly deep, often reaching over 1000m.
What do fjords contain? What causes these?
Contain thresholds.
These are caused by a thinner glacial layer producing reduced rates of erosion.
What is a fjord threshold?
Shallow sections at the front of the fjord entrance.
Give an example of a fjord.
Sogne Fjord in Norway.
(~200km long).
What does wave action do to a rias valley sides?
Increase steepness, but this has limited significance.
What does wave action do to a fjords valley sides?
Wave action (along with weathering) reduces steepness.
There has been a 0.6m eustatic sea level rise in 100 years. What does this mean for the modification of rias and fjords?
There has been a 0.6m eustatic sea level rise in 100 years.
This means there are more storms, so consequently increased erosion.
What is there always the potential for, during the modification of rias and fjords?
There is always the potential for mass movement.
How does a shingle beach form?
Sediment accumulates on this surface, deposited by rivers, meltwater streams and low-energy waves.
As sea levels rose at the end of the last glacial period, wave action pushed these sediments onshore.
In some places, what may form instead of a shingle beach? Give an example.
In some places, they beached at the bases of former cliff lines; elsewhere they may form tombolos and bars.
For example, the tombolo at Chesil Beach is thought to have formed in this way during the Flandrian Transgression. Sediment carried into the English Channel by meltwater during the Würm glacial accumulated in locations such as Lyme Bay.
What do shingle beaches do? What are they composed of?
Shingle beaches remove and/ or bring sediment.
They are composed of unconsolidated material, and are especially vulnerable to modification.
What has the tombolo at Chesil Beach been affected by?
Significantly affected by present day longshore drift processes and is likely to continue to be so in the future.
Recent storms have seen waves over-topping the beach.
What happened to Chesil beach in 2009? Is this common?
In 2009, 1 metre-sized pieces of shelly clay were eroded from in front of the beach and washed up onto it at West Bexington in a winter storm.
With higher sea levels and more frequent storm events this sort of sediment accumulation will become common.
