Coasts EQ1 - Coastal landscapes and processes

Question 1

What is the littoral zone?

Answer 1

Dynamic zone of rapid change - the wider coastal zone where land is subject to wave action

Offshore: The area of deeper water beyond the point at which waves begin to break. Friction between the waves and the sea bed may cause some distortion of the wave shape.
Nearshore: The area of shallow water beyond the low tide mark, within which friction between the seabed and waves distorts the wave sufficiently to cause it to break. (breaker zone) There may be a breakpoint bar between the offshore and nearshore zones.
Foreshore: The area between the high tide and the low tide mark.
Backshore: The area above the high tide mark, affected by wave action only during major storm events.

Question 2

What are the 2 main types of coast?

Answer 2

Rocky - cliffs formed from rocks varying in height (resistant geology, high energy environment)
Coastal plains - land gradually slopes towards sea across area of deposited sediment (high sediment supply, low energy environment)

Question 3

What are the 4 areas in the littoral zone?

Answer 3

Backshore, foreshore, nearshore, offshore

Question 4

What are primary coasts?

Answer 4

Coastlines dominated by land-based processes such as deposition at the coast from rivers, or new coastal land formed from lava flows

Question 5

What are secondary coasts?

Answer 5

Coastlines dominated by marine erosion or deposition processes

Question 6

What is the difference between emergent and submergent coasts?

Answer 6

Emergent - coasts rising relative to sea level (e.g. due to tectonic uplift)
Submergent - coasts being flooded by the sea (due to rising sea levels or subsiding land)

Question 7

What are the three types of tidal range?

Answer 7

• microtidal (0-2m)
• mesotidal (2-4m)
• macrotidal (>4m)

Question 8

What is the difference between low energy and high energy coasts?

Answer 8

Low energy = sheltered, limited wave fetch, low wind speeds mean smaller waves
High energy = exposed, facing prevailing winds, long wave fetches result in powerful waves

Question 9

What is a cliff profile?

Answer 9

The height and angle of a cliff face as well as its features such as wave-cut notches or changes in slope angle

Question 10

What sub-aerial processes act on cliffs?

Answer 10

• weathering
• mass movement
• surface runoff

Question 11

What is rock erosion resistance influenced by?

Answer 11

• how reactive minerals in the rock are when exposed to chemical weathering
• whether rocks are clastic or crystalline (crystalline = more erosion resistant)
• degree to which rocks have cracks, fractures and fissures

Question 12

How are coastal plains maintained in a state of dynamic equilibrium?

Answer 12

2 balancing forces:
- deposition of sediment from rivers inland, and deposition of sediment from offshore/longshore sources
- erosion by marine action at the coast

Question 13

What is coastal accretion?

Answer 13

The deposition of sediment at the coast and the seaward growth of the coastline, creating new land

Question 14

What is dynamic equilibrium?

Answer 14

The balanced state of a system when inputs and outputs are balanced over time. By a process of feedback, the system can adjust to changes to regain equilibrium

Question 15

What is geological structure?

Answer 15

The arrangement of rocks in three dimensions

Question 16

What are the key elements to geological structure and what do they mean?

Answer 16

Jointing - division of rocks into blocks with regular shape
Dip - angle of rock strata in relation to horizontal
Faulting - weaknesses in rock layers (fractures)
Folding - crustal compression where horizontal strata are squeezed

Question 17

What are concordant and discordant coastlines?

Answer 17

Concordant - rock strata run parallel to the coastline
Discordant - different rock strata intersect the coast at an angle

Question 18

How are headlands and bays formed at discordant coastlines?

Answer 18

Softer rock eroded faster - creating bays (differential erosion)
Wave refraction means lateral erosion occurs at headlands (cave arch stack stump), while wave energy in bays is much lower and erosion is reduced

Question 19

How do coves form on concordant coastlines?

Answer 19

More resistant rock broken through by marine erosion, and the softer rock behind is then rapidly eroded to form wide coves. At the back of the coves is more resistant rock which prevents erosion further inland

Question 20

What is a Dalmatian coastline?

Answer 20

Coastline made up of anticlines and synclines that has been drowned by rising sea levels, creating concordant coastline of long narrow islands arranged in long lines offshore

Question 21

What is a Haff coastline?

Answer 21

A concordant coastline where long sediment ridges topped by sand dunes run parallel to the coast offshore, creating lagoons between ridges and shore

Question 22

What is strata?

Answer 22

The different layers of rock within an area and how they relate to each other

Question 23

What 2 geological factors affect cliff profiles?

Answer 23

• the resistance to erosion of the rock
• the dip of rock strata in relation to the coastline

Question 24

What is dip, and why is it important in determining cliff profiles?

Answer 24

Dip is the angle of rock strata in relation to the horizontal (tectonic feature)
It is important as determines the stability of the cliff

Question 25

What are the different types of dip, which is the most/least stable?

Answer 25

• horizontal dip (vertical profile)
• seaward dip (very vulnerable to erosion)
• landward dip (steep profile but stable cliff with reduced rock falls)

Question 26

What are joints?

Answer 26

Joints divide rock strata up into blocks with a regular shape

Question 27

What are fissures?

Answer 27

Much smaller cracks in rocks, often only a few centimetres or millimteres long

Question 28

How does folding occur and how does it create anticlines and synclines?

Answer 28

Folding occurs due to crustal compression - when horizontal strata are ‘squeezed’ they can be folded into a series of anticlines and synclines.
Anticlines - A shaped (convex up)
Synclines - U shaped (concave down)

Question 29

What are faults?

Answer 29

Major fractures in rocks produced by tectonic forces and involving the displacement of rocks on either side of the fault line

Question 30

What is unconsolidated sediment?

Answer 30

Material such as sand, gravel, clay and silt that has not been compacted and cemented to become sedimentary rock, so is loose and easily eroded

Question 31

What is igneous rock (give examples) and what is it’s erosion rate?

Answer 31

Igneous rock is formed from the cooling and solidification of magma - e.g. granite or basalt
VERY SLOW rate of erosion (< 1mm a year) - as they are crystalline and have few joints, interlocking crystals

Question 32

What is metamorphic rock (give examples) and what is it’s erosion rate?

Answer 32

Metamorphic rocks are rocks that have become changed by intense heat or pressure while forming. e.g. slate, marble
SLOW erosion rate (1mm to 10 cm per year) - some are crystalline, others are folded and heavily fractured

Question 33

What is sedimentary rock (give examples) and what is it’s erosion rate?

Answer 33

Sedimentary rocks are formed from pre-existing rocks or pieces of once-living organisms. e.g. sandstone, limestone
MODERATE TO FAST erosion rate (10cm to several metres) - often clastic, and have many bedding planes and fractures

Question 34

What is the difference between impermeable and permeable rocks?

Answer 34

Permeable - allow water to flow through them
Impermeable - do not allow groundwater flow

Question 35

What is pore water pressure?

Answer 35

The pressure water experiences at a particular point below the water table due to the weight of water above

Question 36

How does vegetation stabilise sediment?

Answer 36

• Roots of plants bind sediment particles together making them harder to erode
• When submerged, plants growing in sediment providing a protective layer (surface of sediment not exposed to moving water)
• Plants reduce wind speed to reduce wind erosion because of friction with vegetation

Question 37

What is the difference between halophytes and xerophytes?

Answer 37

Halophytes - tolerate salty conditions
Xerophytes - can tolerate very dry conditions

Question 38

What is a psammosere and a halosere?

Answer 38

Psammosere - sand dune ecosystem
Halosere - salt marsh ecosystem

Question 39

What are the stages in sand dune succession?

Answer 39

• embryo dunes
• fore dunes
• yellow dunes
• fixed dunes (grey)
• heath/woodland

Question 40

What are the roles of embryo dune pioneer plants?

Answer 40

• stabilise mobile sand with their root systems
• reduce wind speeds at the sand surface, allowing more sand to be deposited
• add dead organic matter to the sand, beginning the process of soil formation

Question 41

Why are sand dunes a dynamic environment?

Answer 41

• periods of wind erosion can create low areas within dune systems called dune slacks
• embryo and fore dunes are prone to wind and wave erosion, particularly during major storms, but the dune front will stabilise as long as the supply of sediment to the coast resumes

Question 42

Why are estuaries ideal for the development of salt marshes?

Answer 42

• sheltered from strong waves so sediment can be deposited
• rivers transport a supply of sediment to river mouth, which may be added to by sediment flowing into an estuary at high tide

Question 43

What are the stages in salt marsh succession?

Answer 43

Algal stage - algae grows on and within bare mud, binding it together
Pioneer stage - roots begin to stabilise mud
Establishment stage - continuous carpet of vegetation established
Stabilisation - area of salt marsh rarely submerged
Climax vegetation - developed soil profile, only submerged once or twice each year, land plants can colonise (rainwater washes salt out of soil)

Question 44

What is the difference between permeable and impermeable rock?

Answer 44

Permeable = allow water to flow through them
Impermeable = do not allow water to flow through them
Permeable rocks tend to be less resistant to weathering because water percolating comes into contact with a large surface area that can be chemically weathered.

Question 45

What is the effect of pore water pressure?

Answer 45

Produces slumping and sliding
Pushes rock particles apart, reduces friction between grains in unconsolidated sediment, lubricates lines of weakness

Question 46

Where are complex cliff profiles produced?

Answer 46

In cliffs with strata of differing lithology
Differential erosion rates leads to formation of features like wave cut notches/overhangs