地理漫步·世界地理英语30篇（4）
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The Amazon Fan: Submarine Sediment Accumulation and Deep-Sea Biodiversity Corridors
亚马逊扇：海底沉积堆积与深海生物多样性廊道
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This massive underwater deposit extends over eight hundred kilometers into the South Atlantic Ocean.
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Sediment from the Amazon River settles in layers shaped by turbidity currents and bottom-water density flows.
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Graded bedding reveals episodic flood events that transport clay, silt, and organic matter offshore.
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Cold, oxygen-rich Antarctic Bottom Water flows over the fan, supporting chemosynthetic communities near seeps.
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Submarine canyons incised into the fan serve as migration pathways for deep-sea fish and crustaceans.
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Benthic biodiversity peaks where fine-grained sediments meet harder substrates near canyon walls.
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Seafloor topography controls current velocity, which in turn regulates particle deposition and nutrient flux.
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Methane hydrates occur beneath the fan’s outer reaches, stabilized by high pressure and low temperature.
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Sediment compaction rates vary with grain size, affecting pore-water chemistry and microbial activity depth profiles.
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Mapping acoustic backscatter helps distinguish sediment types linked to Amazon discharge variability over decades.