Title: Coastal Landscapes Date: 28/04/2017 Aims: To learn about the different ways in which the landscape at coasts can change. To learn about the different features found at coasts (more than NAT 5) To learn about the processes of erosion and deposition.

Lesson starter: You have been given a number of sort cards. You must sort out the words to match with the definitions. Some of the class will never have seen the terms before as they have never studied coasts – but this is a great opportunity to learn. Copy the word and definition once you are sure that it is correct.

Hydraulic Action The force of waves hitting a cliff (or sea wall) compresses water and air into cracks and joints. This increase in pressure may lead to cracks widening and pieces of rock breaking off.

Corrasion Rock fragments may be picked up by waves and thrown against the rock face of cliffs by subsequent waves. Sometimes the softer strata are abraded more than the harder ones, giving a striped appearance. Corrasion is most effective at the base of cliffs.

Wave attrition Rock fragments are worn down into smaller and more rounded pieces. Currents and tidal movements cause the fragments to be swirled around and to grind against each other. This type of erosion produces pebble beaches.

Water- layer weathering Alternative wetting and drying -as happens with the rise and fall of the tides -can disintegrate porous or coarser rock layers. Salt crystals growing in rock spaces can do the same thing.

Corrosion (solution) Salts and acids in sea water can react with rocks , slowly dissolving them away.

Rates of erosion depend on many factors: (Copy this note into your jotters. Use your textbook to help add detail to each of the headings.) 10 mins Waves – strength, frequency, height Weather – frequency of storm conditions Geology of the coastline : -type of rock -orientation of stratification

The FETCH is the distance travelled by waves from one shore to another. The waves hitting the southwest coast of England have a fetch of about ten thousand miles!

CONSTRUCTIVE AND DESTRUCTIVE WAVES Constructive waves These are low energy waves which transport grains of sediment and deposit them on beaches. This type of wave is common in the summer. Destructive waves These are high energy waves which erode sediment from the beach and deposit material further along the coast. They mainly occur during winter and autumn storms. Constructive and destructive waves

SWASH AND BACKWASH Waves break and push sediment obliquely up the beach (SWASH)… … but the returning flow is straight down the beach at right angles to the shoreline (BACKWASH) . Swash and backwash

Quick Revision After your work station task, you should be able to answer the following questions

Q1. What two properties of a headland tell us that the rock is hard? A. It juts out into the sea and is high ground. Q2. What two properties of a bay tell us that the rock is soft? A. It eats back into the land and is lower ground. Q3. On a new cliff coast, what is the first feature caused by erosion? A. Wave cut notches are created initially.

Q4.Cliff retreat creates which feature all along the coast? A. It creates a wave-cut platform. Q5.Why is this only exposed at low tide? A. Erosion only happens between high and low tide marks, and no erosion takes place below LTM. The ‘top’ of the eroded cliff is the WCP, seen only when the tide is lowest.

Headland erosion near Noss Point Caithness The sea is eroding this headland back leaving a wave-cut platform below the waves. Waves continually change the shape of the coastline around Britain. Headlands such as this are produced where the rock type is hard and resistant to erosion and bays where the rock type is softer and deposition dominates. In this slide the sea is a powerful agent of erosion. A scree of eroded rocks can be seen at the base of the cliff and a wave cut platform is visible showing where the previous cliff line was.

Cliffs and Wave Cut Platforms

Geo A geo is a small, narrow, steep-sided channel in a sea cliff. It has been formed by erosion along a line of weakness, such as a joint. Originally it was a cave but, at various stages the roof has collapsed, leaving the inlet. They are found in hard cliff coastlines e.g. Northern Scotland

Geo near Noss Point Caused by hydraulic action at a weakness in the rock. Sometimes the sea can erode the areas of weakness in a cliff line producing long sea inlets such as this.

Geo At Duncansby Head The horizontal bedding planes of sandstone are clearly visible but the sea has exploited the vertical joints in the rock to produce this inlet.

A Blowhole or ‘gloup’ is a funnel shaped depression, linking the cliff top with the sea cave. Continued erosion of a vertical joint at the back of a sea cave may lead to the collapse of the cave’s roof. This usually happens at high tide in stormy weather. Copy this note

Clip on blowholes Bullers of Buchan is an Scottish Example of a blowhole. The Feature is 50m deep!

Coves are a special feature and we will learn about them by looking at a case study of Lulworth Cove.

Lulworth Cove was formed by differential erosion Lulworth Cove was formed by differential erosion. The next slides will explain how this happened.

Copy the diagram and explanation. The geology of Lulworth Cove The hard rock at the coast has been breached. The sea can now get in to erode the softer rock behind, creating the cove. The second layer of hard rock stops the cove growing much larger. hard soft .

ORDNANCE SURVEY MAPWORK 6 You need to be able to recognise coastal erosion landforms from a map. To practice this skill, take a copy of the question sheet and the two O.S. maps and tackle the questions. THEY ARE NOT ALL EASY !!