THE SEALEARNING OUTCOMES

TODAY WE ARE GOING TO LEARN ABOUT THE ACTION OF THE SEA .

AT THE END OF THIS CHAPTER YOU WILL BE ABLE TO DISCUSS THE DIFFERENT WAYS THE SEA CAN ERODE, DEPOSIT AND TRANSPORT ITS LOAD.

YOU WILL BE ABLE TO IDENTIFY MANY OF THE FEATURES FOUND ALONG THE COASTLINE AND DESCRIBE HOW THEY WERE FORMED

THE SEA

• LOOK AT THE MAP IN YOUR GEOGRAPHY BOOK.

• SEAS AND OCEANS ARE REPRESENTED BY THE COLOUR…BLUE

• WHAT PERCENTAGE OF THE WORLD IS SEAS/OCEANS?

FETCH AND WAVES

• NO THIS IS NOT SOMETHING WE DO WITH OUR DOG

• When wind blows over the sea it causes waves• The size of a wave depends on its fetch. The

fetch is the distance a wave travels. The greater the fetch, the larger the waves

How waves erode

• Waves erode in 4 ways1. Hydraulic action2. Abrasion3. Attrition4. Compressed air

waves

• Waves can be constructive or destructive • When a wave breaks on the shore it is called

SWASH• When the wave retreats back to the sea this is

called BACKWASH

The sea erodes the coastline and this is what it creates

1. Cliffs2. Wave-cut platform3. Bays and headlands4. Sea cave5. Sea arch6. Sea stack7. Blow holes

WORKBOOK PAGE 24• COLUMN 1 COLUMN 2A. WAVES THEY CAN BE CONSTRUCTIVE/DESTRUCTIVEB. FETCH IN IRELAND IT HAS SW DIRECTIONC. PREVAILING WIND LENGTH OF SEA OVER WHICH WAVE PASSESD. SIZE OF WAVES INFLUENCED BY STRENGHT OF WIND

COLUMN 1 COLUMN 2 A. SWASH THEY CAN CAUSE EROSION ALONG COASTBACKWASH WATER RUSHING TOWARDS THE SHORECONSTRUCTIVE WAVES WATER MOVING BACK DOWN SHOREDESTRUCTIVE WAVES THEY CAN TRANSPORT AND DEPOSIT

WORKBOOK PAGE 25• COLUMN 1 COCLUMN 2• A. ABRASION WAVES HITTING COAST• B. ATTRITION ROCKS AND STONES ERODING• C. HYDRAULIC ACTION AIR TRAPPED IN CRACKS IN ROCKS• D. COMPRESSED AIR ROCKS BROKEN DOWN AND ROUNDED

• DESCRIBE THE FORMATION OF CLIFF USING FOLLOWING WORDS/CHART• OVERHANG COLLAPSES MATERIAL IS REMOVED PROCESS REPEATED• COASTLINE RETREATS NOTCH IS CUT BY EROSION

LEAVING A CLIFF AND WAVE-HH CUT PLATFORM

Cliffs and wave-cut platforms

cliffs• Cliffs are vertical slopes along the coast

• When the waves hit the coast, rocks are hurled against the cliff wall.

• They create a notch (hole) at the base of the cliff which becomes deeper.

• Eventually the overhanging rock collapses and the cliff retreats back

• Over time it leaves a rock platform called a wave-cut platform

cliffs

Wave cut platform

Bays and headlands

2. BAYS AND HEADLANDS

• A bay is a wide, curved opening into the coast

• A headland is a neck of land that juts out into the sea

How are bays and headlands created?

Sea caves

Sea caves

• A sea cave is a tunnel that is found at the base of a cliff

• The waves attack the rock by hydraulic action, abrasion and compressed air.

• The crack develops into a small cave eventually

Sea arch

Sea arch• When a headland is eroded by the sea, it forms a small cave.

• Erosion continues to enlarge the cave eventually forming a passage way through to the other side of the headland

• Sometimes there can be a cave on both sides of the headland and they meet in the middle to form a sea arch

sea stack/sea stump

A sea stack

• A sea stack is like a large pillar standing in the sea

• It is formed from a sea arch. • The roof of the cave has nothing to support it

so it eventually collapses leaving a pillar called a …………

blowhole

Blowhole

blowholes

• When a cave is formed at the base of a cliff, it is continually eroded by the action of the sea

• The roof of the cave is eroded by rocks and by compressed air.

• Trapped air expands under pressure to cause a mini explosion in the roof of the cave

• Eventually the roof of the cave collapses forming a blowhole

The sea transports its load

• Longshore drift

Longshore Drift

• The waves approach the beach at a 45 degree angle

• The swash deposits the heavier material on the beach

• The lighter material is carried back out to sea by the backwash

• This process is repeated and material is transported along the coast

Features of deposition

• So far we have looked at how the action of the sea causes coastal erosion and transportation called…….what’s that word I told you NOT to remember yesterday

hhhhhmmmm….Long

A beach and a stormbeach• What is a beach????• It is a build up of sand and shingles deposited

between low and hide tide

• What is a stormbeach?• When the weather is stormy the sea has more

energy and it can hurl large stones and rocks even further than normal on the beach

• These rocks are too heavy to be carried by to sea by the backwash so they remain there

What are sandunes??

• Wind and sandblows in from the sea• It dries the sand on the beach making it lighter it can get trapped inVegetation on the beach and it piles up to formSand dunes

Sand dunes with marram grass

The sea deposits its load

• Sand spit

Sand Spit is a feature of depositon

Sand spit in Mexico

What is a sand spit and how is it formed??

• A sand spit is a ridge of sand that extends across a bay

• It is caused by LONGSHORE DRIFT.

• When the coastline changes, longshore drift loses some of its energy and it deposits its load. (it doesn’t have the energy to bring it back out to sea)

• Eventually all the material builds up above sea level

• The process continues and the sand spit extends all the way across the bay to form a SAND BAR

People and the sea

• The sea plays an important role in human activities.

• Can you think of 3 ways the sea is important?

• 1. RecreationA range of activities includes boating, swimming, fishing and sunbathing2. TransportShips can transport bulky cargo across the world. People can travel on car ferries.3. Food supplyFishing provides us with food. It also creates employment for: fisherman, fish processing factories and in workers in fish shops.

Gabions Groynes