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How a Lagoon Is Born

Sea currents carry sand along the coast and drop it across the opening between two hills. Little by little, the sand builds a bar that rises above the water and traps a pocket of sea behind it, called a lagoon.

In the picture

  1. A current flows along the shore carrying sand
  2. Sand piles up under the water in a long ridge
  3. The ridge rises above the waves as a sand bar
  4. Sea water trapped behind the bar becomes a lagoon

Examples

  • A sandbar you can walk out to at low tide forms the same way
  • The Venice lagoon in Italy is kept apart from the sea by long sandy islands

Quiz: How a Lagoon Is Born (Age 11)

  1. What carries the sand that builds a lagoon’s sand bar?

    • Rivers flowing down from the hills
    • Sea currents moving along the coast
    • Strong winds blowing across the beach
  2. Before a sand bar can be seen, where is the sand piling up?

    • On the dry beach, out of the water
    • Far out in the deep open sea
    • Under the water, across the opening
  3. What turns a pocket of sea water into a lagoon?

    • A sand bar rises and traps it behind
    • A river fills a hollow between two hills
    • The tide digs a deep hole in the beach

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Geography, Age 11