Coasts 1

Coasts 1

By Joselito Ebro

Lesson Objectives

• ​Define the following:

  • Coasts

  • Waves​

• Explain how the sea and wind erode, transport and deposit

IGCSE Geography

The land along the sea. The boundary of a coast, where land meets water, is called the coast line.​

Coasts

Open Ended

Using the video, describe the relationship between water and land.

How coasts are formed...

Waves, tides and currents create coastlines as they wear away or erode the land. ​

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Coastal changes can take hundred of years. ​

Marine processes in Coasts

• waves and currents, including longshore drift

• local geology - rock type, structure and strength

• changes in sea level

• human activity and the increased use of coastal engineering​

These factors interact and produce a unique set of processes that occur at the coast. These processes go on to produce different types of landform for every coastal area.

​Wave

Waves

Waves are energy movements through water caused by the wind. They are the main way in which the sea erodes, transports and deposits materials.

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These result from friction between wind and the sea surface.​

Parts of a ​Wave

Parts of a ​Wave

​Wavelength - the distance between two successive crests and troughs. (distance between the trough and crest)

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Wave frequency - the number of waves per minute.

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Velocity - the speed of a travelling wave, and is influenced by wind, fetch and depth of water.​

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Wave Energy

The energy of a wave is determined by its height (between trough and crest) and length (between two crests)

• Wave height and length vary according to the speed and length of time a wave has been moving, and the fetch the distance of open, sea over which the wind has blown.

• Near the coast, waves slow down in the shallow water, causing them to 'break', becoming unstable. Seawater moving up the beach is swash, and then moving back to the sea is backwash.​

Waves can be Constructive or Destructive

• Constructive - operate in calm weather and are about a metre high. The swash is strong and erosion is limited. They're involved with the transport and deposition of material creating landforms.

Waves can be Constructive or Destructive

• ​Destructive - operate in storm conditions and are about 5 or 6 metres high. The backwash is strong and there is a lot of erosion.​

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Open Ended

Contrast destructive and constructive waves.

Some wave characteristics...

• Sea waves are different from those breaking on shore.

• ​Although it appears to move, the water particles follow a roughly circular path within a wave.

• As waves approach the shore, their speed is reduced as they touch the seafloor.​

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Some wave characteristics...

• ​As it moves closer to the shore, two things could happen Wave refraction or longshore drift.

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Wave Refraction

Causes two main changes:

• the speed of the wave is reduced

• the shape of the wavefront is altered​

Wave refraction: the way in which a wave changes shape and loses speed as it comes into contact with the sea bed.

Longshore Drift

The movement of material along a beach by wave action.

• occurs when waves move up to the beach (swash) but the waves draining back down (backwash) take a different route (due to gravity).​

Through these processes, landforms or features are formed.

​Navaré, Portugal

• Navara is a small village on the Western coast of Portugal.

• Its known for huge waves that swept through its shores

• In 2011, Garrett McNamara rode a 78-foot wave which remains the world record for big wave in surfing

Navare Waves

Activity (Trio Activity)

• Work with your groupmates and investigate why are there such big waves in Navaré, Portugal.

• Your explanation should include 2-3 concepts that we have studied today.

• Make a one-minute video that shares your research.

• Be creative in making your video. Your group is free to use illustrations, materials, etc found in the classroom.

Video Response

Share your videos here. :)

Open Video Recorder