地理漫步·世界地理英语30篇（4）

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贝加尔湖：世界最深最古老的淡水裂谷湖

Lake Baikal lies in a tectonic rift valley where the Eurasian Plate slowly pulls apart.
At 1,642 meters deep, it holds 20% of Earth’s unfrozen freshwater and formed over 25 million years ago.
Its isolation and stable cold climate allowed unique species like the Baikal seal to evolve nowhere else.
Underwater faults and hydrothermal vents sustain chemosynthetic communities far below sunlight zones.
Sediment layers in its basin preserve continuous climate records spanning millions of years.
Waters remain exceptionally clear due to endemic crustaceans that filter algae year-round.
The Selenga River contributes half the inflow but also carries mining runoff threatening water quality.
Winter ice cover reaches one meter thick, yet cracks form predictable patterns revealing subsurface stress fields.
Local communities rely on fisheries and eco-tourism, both constrained by strict UNESCO World Heritage protections.
Climate warming accelerates ice melt, altering thermal stratification and disrupting endemic food webs.