The Work of the Sea

Erosion – rocks are worn down and broken into smaller rocks

Transportation – rocks and sand are moved from one area to another by waves and sea currents

Deposition – material is deposited (dropped) in some areas, forming beaches and sand dunes

Processes at work in the Sea

Hydraulic Action – force of moving water Compressed Air – air gets trapped in rock, the pressure

of the air can crack rock Abrasion – rocks and stones can be thrown against the

coastline, wearing it away Attrition – rocks and stones are worn down themselves

How Waves Erode

Name the erosion process?

Formation of Bays and Headlands

The hard rock in a coastline erodes more slowly than the soft rock

The hard rock that has not eroded, juts out to the sea, forms a headland. The spaces between the hard rock are known as Bays

BAY

BAY

Headlands

Sea Cliffs – Cliffs of Moher

Formation of Cliffs – steep parts of the coast

A Cliff is formed when◦ Waves erode the coast and form a small notch.◦ The erosion continues until the notch gets bigger. ◦ The section of rock above the notch cannot be supported

anymore and collapses.◦ The slope becomes steeper◦ A cliff is formed.

◦ The former base of the cliff remains as a wave cut platform.

Sea Caves, Sea Arches, Sea Stacks

Formation of Sea Caves

A large hole or tunnel at

the base of the Cliff is

called a cave. If there is a weak spot

such as a crack or a joint

in the rock, the waves will

attack it and erode a

passage called a sea cave

If a Cave erodes right through a headland (or if two caves erode from each side) an arch is formed

If the roof of an arch collapses, a sea stack is formed The sea stack can eventually be eroded down to a

stump.

Formation of Sea Arches

Sea Stack

Formation of a Blow Hole

Draw diagram p54

• A blow Hole is a hole which joins the roof of a cave with the surface above.

2011 Junior Cert

Transportation by the Sea

Waves approach the shore at an angle. The swash of each wave pushes material up the beach (A-B). Because of the slant the backwash drags the material straight

down (B-C) The process is repeated so the material is transported (moved)

along in a zig zag pattern.

Long Shore Drift

How can you stop Long Shore Drift?

A Groyne is a low wall built into the sea to stop long shore drift.

Sea Deposition

A beach is a gently sloping area of sand, pebbles or stones along the shore.

It lies between the high-tide mark and the low-tide mark.

It is formed by the swash pushing materials up the beach and the weaker backwash pulls finer materials back down.

Formation of a Beach:

A Storm Beach is formed when large stones are deposited at the top of a beach during a storm.

Sand Dunes

Sand dunes are mounds of sand at the back of a beach.

Sand dunes are formed because of the wind blowing the sand inland.

Marram Grass

Marram grass is long, dry and has long roots.

These roots bind the sand together and protect it from the wind and the rain

The Formation of a SPIT

A sand spit is a ridge of sand or shingle that juts out into the sea.

Long shore drift stops when it reaches a bay or sheltered place.

The material may build up gradually to form a spit.

Eg. Portmarnock, Co. Dublin

The formation of a SPIT

Formation of a SAND BAR

A sand bar is a sand spit (explain formation) that stretches across a bay to connect the two sides of the bay.

The lake behind the sand bar is called a lagoon

Example: Lady’s Island, Co. Wexford

Formation of a SAND BAR

Formation of a TOMBOLO

A tombolo is a ridge of sand or shingle that joins an island to the mainland

A tombolo forms when a sand spit juts out into the sea and links with an island

Example: Sutton, Co Dublin

Formation of a TOMBOLO

2012 Ordinary Level Junior Cert

2011 Higher Level Junior Cert

2010 Junior Cert Higher Level

Defence: Protecting land and people from erosion

Economic activities: Making money from the sea and its resources.

Interaction with the Sea

Made of Reinforced Concrete Stops waves from eroding land away Has NO effect on Longshore drift Expensive to build

Defence – Sea Walls

Also known as “Rock Armour” Simple to build, cheap Can cause safety concerns and look ugly Has NO effect on longshore drift

Defence - Boulders

Low walls, built at right angles to the coast Made of wood (cheap) or concrete (expensive) Reduce longshore drift

Defence - Groynes

“Walls” made of wire mesh filled with stones Reduce Erosion Cheap to build – but can cause safety concerns and do not

last too long

Defence - Gabions

Economic use of the Sea - Fishing

Economic Use of the Sea – Tourism/Recreation

Economic use of the Sea – Wind Energy

Economic use of the Sea – Wave Energy

Economic use of the Sea – Fossil Energy

Litter from people at the coast Overfishing and damage to wildlife Oil Spills and pipe breaks

Misuse of the sea - pollution

2008 Leaving Cert Higher