transportation deposition

Why do we get beaches?

How is material transported?

The sea transports massive amounts of The sea transports massive amounts of rock material around every dayrock material around every day

Some bits are as small as sand, other Some bits are as small as sand, other bits are big pebbles or even bouldersbits are big pebbles or even boulders

Coasts are not just eroded, they are also built up by deposition – this is when eroded material is dropped off and builds up over time

This creates beaches

Deposition happens when waves are constructive (so the swash is bigger than backwash so material gets moved up on to the beach).

Material is moved by the sea and can travel miles

Longshore drift (LSD) is the process where waves transport eroded material along a beach and deposit it down coast

LSD animation

Geog.GCSE p92

Make your own copy of the LSD diagram, with labels

Q)What controls the direction of movement along a beach?

Q)What direction does most material move on the south coast of England?

P93

Q) Why is LSD sometimes a problem?Q) What do we do to stop LSD?

Beaches, spits, bars and tombolos are created by deposition and transportation

Beaches are basically eroded material that has been transported from somewhere else and deposited

P94-95 Write your own summary (just a few

sentences) to explain: - beaches - spits - bars - tombolos

Extension: Answer Q1,3

Revision games:http://www.sharegeography.co.uk/coastspen.html

http://www.sharegeography.co.uk/oldharrymin.html

http://www.bbc.co.uk/schools/gcsebitesize/geography/coastal/

http://www.teachers-direct.co.uk/resources/quiz-busters/quiz-busters-game.aspx?game_id=7127

Find some pictures of beaches, bars, spits and tombolos to stick in to your book.

Beaches Beaches develop when the supply of sediment exceeds any sediment lost through backwash and longshore drift.

Beaches are usually distinguished as either …

ShingleShingle or or SandSand

Shingle beaches are free draining so there is little backwash of material to sea. As a consequence, they are usually steeper.

Some features of a shingle beach ..

... The largest material is found furthest from the sea

Successively lower berms

You get ridges across the beach called berms

Sand beaches Sand beaches have a more have a more gentlegentle profile. profile. This is because....This is because....

Wet sand compacts, so water doesn’t drain through it. This means that backwash, and the material it is carrying, is able to return to the sea.

Sand is smoother than shingle.... so there is less friction to prevent the materials moving back down the beach

These get colonised by grasses and become ecosystems

As on-shore winds blow across dry beach sand, it carries

material inland to form sand dunessand dunes

Spits and BarsSpits and BarsWhere there is a change in the coastline e.g. a headland or an estuary mouth, longshore drift may continue to deposit sediments into the sea forming a spit.

Spurn HeadSpurn Head at the mouth of the Humber estuary is a fine example of a spit.

Local currents and changes in wind direction may curve the end of the spit landwards creating a hooked tip.

The presence of the estuary discharging river water into the sea prevents the spit from developing into a bar.

Such a feature is known as a recurved spitrecurved spit

wind

If a spit joins on to one part of the mainland to another it is

called a barbar.

For example, there is a bar at Slapton SandsSlapton Sands in Devon.

TomboloTombolo

Where a spit joins the mainland to an island a tombolo may be created .

The longest and best known tombolo in Britain is

Chesil BeachChesil Beach.

Chesil Beach viewed from the Isle of Portland