Mon Prof Augmenté
The Sinking Delta Town
Age 16 · Environmental Science
A river delta is built from layers of soft, water-filled mud that slowly squeeze together and sink under their own weight. At the same time the sea rises, so towns built on the delta can end up underwater.
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Age 16: open this week
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In the picture
- Layers of river mud: soft silt full of water, laid down by floods
- Mud blocks breaking and sliding seaward: the squeezed ground sinks and cracks
- A higher sea surface: rising water reaches further up the shore
- Tilted temple columns on the seabed: a town lost as the ground went down
Examples
- Venice, built on muddy lagoon islands, floods more often as the ground sinks and the sea rises.
- Parts of the Nile and Mississippi deltas are sinking while their coastlines shrink.
Key takeaways
- Waterlogged silt compacts under its own weight, so the land surface slowly drops.
- Sinking land plus rising sea makes the water rise faster against the town than the sea alone would.
Quiz: The Sinking Delta Town (Age 16)
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Why does the land surface of a river delta slowly drop over time?
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A delta town’s land is sinking while the sea is also rising. How fast does the water rise against the town?
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What is the ground of a river delta mainly made of?
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