Geological Structure and Coastal Landscape Flashcards Preview

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Flashcards in Geological Structure and Coastal Landscape Deck (24)
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1
Q

Geological Structure

A

The arrangement of rocks in 3 dimensions

2
Q

3 Key elements in geological structure

A
  • strata: different layers of rock within an area and how they relate to each other
  • Deformation: the degree ti which rock units have been deformed by tectonic activity
  • Faulting: the presence of major fractures that have moved rocks from their original positions
3
Q

What are the 2 dominant types of coast produced by geological structure?

A

Concordant and Discordant

4
Q

Concordant Coasts

A

Generated when rock strata run parallel to the coastline

5
Q

Discordant Coasts

A

Form when different rock strata intersect the coast at an angle

6
Q

Features of concordant coasts

A
  • Strata run parallel to the coastline but vary in terms of their resistance
  • Hard rock protect softer, landward rock. Resistant chalk prevent inland erosion.
  • marine erosion can break through resistant beds, and erode coves behind.
7
Q

Examples of concordant coasts

A
  • Lulworth coast, Dorset
  • Dalmatia Coast, Croatia - limestone, folded by tectonic activity into anticlines and synclines, drowned by water from the holocene, creates concordant coastline of islands.
  • Haff coastlines - sediment ridges topped with sand dunes create lagoons between ridges and the shore.
8
Q

Holocene

A

The geological epoch that began about 12,000 years ago at the end of the last ice age. Its early stages were marked by large sea level rises of about 35m and a warming interglacial climate

9
Q

Features of discordant coasts

A
  • Dominated by headlands and bays
  • Headlands form when weak rocks are eroded and more resistant rocks form headlands. Headlands eroded more than bays, reduces difference between headlands and bays and the coast smoothes out over time.
10
Q

How do discordant coasts effect wave crests?

A
  • In deep water, wave crests are parallel
  • As waves approach the shallower water offshore of a headland, they slow down and wave height increases
  • In bays, wave crests curve to fill the bay and wave height decreases.
  • Straight wave crests refract, becoming curved, spreading out in the bay and focusing on headlands.
  • Overall effect: Powerful waves concentrated on headlands, so greater erosion. Lower, diverging we crests in bays, so less erosion.
11
Q

Examples of discordant coasts

A

West Cork Ireland

12
Q

What 2 main factors influence cliff profiles?

A
  • The erosion resistance of the rock

- The dip of rock strata in relation to the coastline

13
Q

What is dip?

A

The angle of rock strata in relation to the horizontal. Tectonic feature. Sedimentary rocks formed in horizontal layers, can be tilted by plate tectonic forces.

14
Q

Horizontal Dip

A

Vertical or near vertical cliff profile with notches, reflecting where strata are more easily eroded.

15
Q

Seaward Dip High Angle

A

Sloping, low angle profile with one rock layer facing the sea, vulnerable to rock slides down the slope

16
Q

Seaward Dip Low Angle

A

Profile may exceed 90 degrees producing areas overhanging rock, very vulnerable to rock falls.

17
Q

Landward dip

A

Steep profiles of 70-80 degrees producing a stable cliff with reduced rock falls.

18
Q

Which other geological factors influence cliff profiles and rates of erosion other than dip of strata?

A
  • Faults
  • Joints
  • Fissures
19
Q

Faults

A

Major fractures in rocks produced by tectonic forces and involving the displacement of rocks on either side of the fault line. Rocks either side of fault line are heavily fractured and broken, weaknesses are exploited by marine erosion.

20
Q

Joints

A

Occur in most rocks, often in regular patterns, dividing rock into blocks with regular shape.

21
Q

Fissures

A

Much smaller cracks in rocks, often only a few cm or mm long, represent weaknesses which erosion can exploit.

22
Q

Wave refraction

A

The process causing wave crests to become curved as they approach a coastline.

23
Q

Micro features

A

Small scale coastal features such as caves and wave cut notches which form part of a coastline

24
Q

Anticlines and synclines

A

Geological fold, caused by tectonic compression. Anticlines form crests and synclines form troughs.