地理漫步·世界地理英语30篇（1）
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Caspian Sea: A Landlocked Body with Marine Characteristics
里海到底是湖还是海
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The Caspian Sea is Earth’s largest inland body of water, covering 371,000 square kilometers but lacking oceanic connection.
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Its salinity averages 1.2%, one-third that of seawater, varying from fresh near Volga inflows to brackish in southern basins.
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Tectonic origin distinguishes it from lakes—it sits in a remnant oceanic basin formed by the collision of Arabian and Eurasian plates.
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Unlike true lakes, it has marine species like sturgeon and endemic plankton adapted to fluctuating salinity and pressure gradients.
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Sea-level changes—up to three meters since the 1970s—reflect climate-driven evaporation and altered river inputs from the Volga and Ural.
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Oil and gas platforms operate offshore using marine drilling standards, though jurisdiction falls under littoral state treaties rather than UNCLOS.
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Sediment cores reveal ancient marine fossils, confirming its Pliocene connection to the Paratethys Sea before isolation.
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Its stratified water column features oxygen-rich surface layers and anoxic deep basins over 1,000 meters deep.
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Coastal management requires transnational coordination because shoreline erosion in Turkmenistan affects sediment supply to Kazakh deltas.
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Geographers classify it as a 'sea' functionally due to size, hydrodynamics, and biogeography—even if legally defined as a lake by some states.