Land with sea on three sides
What Is a Peninsula?
A peninsula sticks out into the water, and living on one changes almost everything about a place.
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Step 1 of 5
It is nearly an island.
An island has water all the way round. A peninsula has water on three sides and one land connection — which is the difference between needing a boat and not.
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Step 2 of 5
Sticking out makes an enormous coast.
A square lump of land has four short edges. Stretch it into a finger and the coastline grows far faster than the area does, so a peninsula is nearly all coast.
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Step 3 of 5
The sea keeps it mild.
Water warms and cools far more slowly than land. Sea on three sides means summers are cooler and winters milder than the same place inland would be.
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Step 4 of 5
They form in a few different ways.
Some are ridges of hard rock the sea has not worn through. Some are sandbars built up by currents. Some are simply high ground left over as the sea rose around it.
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Step 5 of 5
A narrow neck is a chokepoint.
Everything travelling by land has to pass the join. Those necks have been fortified, taxed and fought over for as long as there have been roads.
Where the neck is narrow enough, people have simply cut through it. That is what a ship canal is: a peninsula turned into an island on purpose.
The short version
A peninsula is land with sea on three sides, which gives it a mild climate, a huge coastline and one narrow way in by land.
Try it yourself
Find a peninsula on a map and trace its coast with a finger, then its land border. The difference is the point.