The Work of the Sea
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Transcript of The Work of the Sea
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