Coasts on the Move
Waves take material from one part of a coast and put it down further along, so beaches, spits and bars are all sediment in transit. A coastline is a balance sheet that never quite settles.
What a learner can do afterwards
- Explain how waves arriving at an angle move sediment along a beach
- Say how a headland and a bay form on a coast made of alternating hard and soft rock
- Name one coastal landform made by erosion and one made by deposition
1 · Read
Waves that hit at an angle push sand sideways along the shore. That zigzag trip has a name: longshore drift.
Soft rock wears back fast into curved bays, while tough rock juts out as headlands. Erosion builds cliffs, caves, arches and stacks, while dropping builds beaches, spits and bars.
Sand piles at one end of a beach because drift feeds it there. Block the drift with a wall and the beach further along starves.
People defend shores with hard walls that block wave force, or soft plant buffers that trap sand and drink up wave force.
Waves move sand along, carve the soft rock first, and drop new land where they slow.
2 · Watch
Take it off screen
Where it sits
8 questions wait behind this lesson, each with its answer explained. Every answer feeds the sky: stars light as they are learned, and dim when it is time to come back.