Depression (geology)
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In geology, a depression is a landform sunken or depressed below the surrounding area. Depressions form by various mechanisms.
A watering hole is a natural depression where water collects and animals come to drink.
Karst closed depression with permanent lake Stymfalia, Peloponnese, Greece. Seasonal abundant precipitation drained by 3 sinkholes
Caspian Depression
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The Caspian Depression or Pricaspian/Peri-Caspian Depression/Lowland is a low-lying flatland region encompassing the northern part of the Caspian Sea, the largest enclosed body of water on Earth. It is the larger northern part of the wider Aral-Caspian Depression around the Aral and Caspian Seas.
Caspian Depression and north Caspian Sea from space. NASA photo