Lecture 5-Rocky Coast Geomorphology I

Question 1

What is coastal geomorphology?

Answer 1

-study of development and evolution of the coast as it acts under the influence of interacting physical processes

Question 2

What are some examples of physical processes in the sea?

Answer 2

-winds, waves, currents, and sea-level changes

Question 3

Can change in coastal processes and landforms affect the habitats and biota on the coastline?

Answer 3

-yes

Question 4

What are the boundaries of a shore platform?

Answer 4

–defined as area of cliff, between landward cliff and seward cliff

Question 5

What is the definition of a shore platform?

Answer 5

-An erosional bench found on rock shorelines -degrade over time -found on rocky shorelines

Question 6

What does the form of the shore platform depend on?

Answer 6

1.Tidal range 2.Rock type (efers to hardness or softness of the rock -structure of the rock (cracks or not etc.) 3.Relative dominance of waves and tides: -waves= high energy (concentrated on the sea bit), short term -tide= lower energy ,but always acting)

Question 7

What are the three types of tidal ranges and what is a tidal range?

Answer 7

-difference between water level at low tide and high tide 1. microtidal under 2m 2. mesotideal 2-4m 3. macrotidal 4m and above

Question 8

What are the three main geomorphic forms?

Answer 8

Type A, Type B and Plunging Cliffs

Question 9

What is the Type A shore platform?

Answer 9

-sloping in seaward direction -little change in gradient at high or low level tide, as the water covers it all -wave energy progressively decreases towards the landward cliff -little change in wave energy under storms

Question 10

What are the three model for evolution of Type A shore platform?

Answer 10

1.vertical erosion: 5 stages, initial stages, cliff profile as it is, as waves go= undercut the cliff 2.horizintal erosion model= characteristic step or notch in the cliff 3.simultaneous model= both horizontally and vertically

Question 11

What are the characteristics of Type B shore platform?

Answer 11

-Flat surface and step or cliff that drops off into the sea, lot of the energy from waves concentrated on seaward cliff -Have a sub horizontal surface -Distinct break in slope at the seaward edge, termed a seaward cliff (sometimes called a low tide cliff, but that suggests an elevation) -Wave energy concentrated on seaward edge -Wave energy variable under storms & also tide (depending on elevation)

Question 12

How does the Type B shore platform evolve?

Answer 12

-weathered rock on the top and unweathered rock under, first stage of erosion: initial sea cliff formed -over time erosion occurs and shore platform forms, as the unweathered rock is also exposed -sewards side= there is still a little step= from the past of the cliff, the first step -Width of platform dependant on rate of landward movement of both landward & seaward cliff

Question 13

What are the characteristics of the Plunging Cliff?

Answer 13

-no platform development -rock shoreline goes deep down into deep water (plunges in) -little wave breaking -due to the morphology of the rock= doesn’t present much of a chance for waves to break -debate on how much erosion and how fast it is happening

Question 14

How does tidal range act as a factor in determining the form of shore platforms?

Answer 14

-tide determines how long the waves or the water will act upon the platform -higher tide= longer time and vcice versa with low tide -Tidal exposure= how long the rock exposed to tide (just types A and B) -Type A characteristics of macro tidal areas, has wider range of tides Type B of microtidal areas (the grey box) so smaller tidal range -smaller tidal range= smaller platform gradients

Question 15

How does rock type act as a factor in determining the form of shore platforms?

Answer 15

-important factor- the erodability of the rock -on top= evolution of rock platform with soft rock and hard rock on the bottom -bottom= less energy in wave, results in steeper gradient, -total energy expended on the platform is a product of rock type and energy per wave -harder rock= needs more energy and time to erode -most of the rock high up in the cliff probably harder as it didn’t erode as much -fractures accelerate erosion (not just cracks but also bubbles, micro-cracks, rock pools can create turbulence)

Question 16

How does relative dominance of waves & tides vrs weathering act as a factor in determining the form of shore platforms?

Answer 16

-wave shoaling -after wave breaking processes, the surface is exposed to waves and weathering, also subareal weathering, = hogh speed winds, -also transport of salt- can erode the rock chemically and mechanically -small bits of rock fall of= creation of sand -wave activity will actively break up the platform, plus the turbulence will work to transport the rock offshore -will remove any loose debris -not only erosion also -wetting and drying cycles: important for life, wet in high tide, dry in low tide -at higher tidal elevation (macrotidal area) as the time difference between high and low longer so the effects of it are more profound

Question 17

What is wave shoaling?

Answer 17

the effect by which surface waves entering shallower water increase in wave height (which is about twice the amplitude). It is caused by the fact that the group velocity, which is also the wave-energy transport velocity, decreases with the reduction of water depth.

Question 18

What do the three factors (tidal range, rock type, relative dominance of waves & tides vrs weathering ) do in forming the platform?

Answer 18

-These three factors combined= on the small scale to produce a complexity of habitats -provide places to live for organisms -get a range of microhabitats -depends on the individual setting of the platform -hardened cliff faces -notches= start of an erosion(may collapse), notch at the base of the cliff -abrasion ramp= rough areas, -further offshore- scarplet -then honeycomb weathering= good for shells -mesa= raised platform of rock formed by erosive patterns -rampart= can protect the things loving on the slide - -location of boulders, usually close to the land as the waves and tides don’t often reach that far to move them= that is why you get rock pools etc. -seaweed common on platforms