Geological Structure and Coastal Landscape

Question 1

Geological Structure

Answer 1

The arrangement of rocks in 3 dimensions

Question 2

3 Key elements in geological structure

Answer 2

• 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

Question 3

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

Answer 3

Concordant and Discordant

Question 4

Concordant Coasts

Answer 4

Generated when rock strata run parallel to the coastline

Question 5

Discordant Coasts

Answer 5

Form when different rock strata intersect the coast at an angle

Question 6

Features of concordant coasts

Answer 6

• 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.

Question 7

Examples of concordant coasts

Answer 7

• 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.

Question 8

Holocene

Answer 8

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

Question 9

Features of discordant coasts

Answer 9

• 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.

Question 10

How do discordant coasts effect wave crests?

Answer 10

• 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.

Question 11

Examples of discordant coasts

Answer 11

West Cork Ireland

Question 12

What 2 main factors influence cliff profiles?

Answer 12

• The erosion resistance of the rock

- The dip of rock strata in relation to the coastline

Question 13

What is dip?

Answer 13

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.

Question 14

Horizontal Dip

Answer 14

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

Question 15

Seaward Dip High Angle

Answer 15

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

Question 16

Seaward Dip Low Angle

Answer 16

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

Question 17

Landward dip

Answer 17

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

Question 18

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

Answer 18

• Faults
• Joints
• Fissures

Question 19

Faults

Answer 19

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.

Question 20

Joints

Answer 20

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

Question 21

Fissures

Answer 21

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

Question 22

Wave refraction

Answer 22

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

Question 23

Micro features

Answer 23

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

Question 24

Anticlines and synclines

Answer 24

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