Cliff profiles Flashcards
What is a cliff profile?
A cliff profile is the height and angle of a cliff face, plus its features such as wave-cut notches or changes in slope angle.
Cliff profiles are influenced by geology. Which two characters are dominant?
The resistance to erosion of the rock.
The dip of rock strata in relation to the coastline.
What type of feature is a dip?
Tectonic
Effect of a horizontal dip on a cliff
Vertical or near-vertical profile with notches reflecting strata that are more easily eroded
Effect of a seaward dip high angle
Sloping, low-angle profile with one rock layer facing the sea; vulnerable to rock slides down the dip slope.
Effect of a seaward dip low angle
Profile may exceed 90 degrees producing areas of overhanging rock; very vulnerable to rock falls.
Effect of landward dip
Steep profiles on 70-80 degrees and producing a very stable cliff with reduced rock falls.
What are faults?
Faults are major features in rocks produced by tectonic forces and involve displacement of rocks on either side of the fault line.
What are micro-features?
Micro-features are small-scale coastal features such as caves and wave-cut notches which form part of a cliff profile.
What factors influence cliff profiles and rates of erosion?
Faults
Joints
Fissures
Folded rocks
How do faults influence cliff profiles and rates of erosion?
Faults: Either side of a fault line, rocks are often heavily fractured and broken and these weaknesses are exploited by marine erosion
How do joints influence cliff profiles and rates of erosion?
Joints occur in most rocks, often in regular patterns, dividing rock strata up into blocks with a regular shape.
How do fissures influence cliff profiles and rates of erosion?
Fissures: Much smaller cracks in rocks, often only a few centimeters or millimeters long but they also represent weaknesses that erosion can exploit.
How do folded rocks influence cliff profiles and rates of erosion?
Folded rocks: Often heavily fissured and jointed, meaning they are more easily eroded.
What are the locations of micro-features controlled by?
Location of faults and/or strata which have a particularly high density of joins and fissures.
