地理漫步·世界地理英语30篇（4）

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亚马逊扇：海底沉积堆积与深海生物多样性廊道

This massive underwater deposit extends over eight hundred kilometers into the South Atlantic Ocean.
Sediment from the Amazon River settles in layers shaped by turbidity currents and bottom-water density flows.
Graded bedding reveals episodic flood events that transport clay, silt, and organic matter offshore.
Cold, oxygen-rich Antarctic Bottom Water flows over the fan, supporting chemosynthetic communities near seeps.
Submarine canyons incised into the fan serve as migration pathways for deep-sea fish and crustaceans.
Benthic biodiversity peaks where fine-grained sediments meet harder substrates near canyon walls.
Seafloor topography controls current velocity, which in turn regulates particle deposition and nutrient flux.
Methane hydrates occur beneath the fan’s outer reaches, stabilized by high pressure and low temperature.
Sediment compaction rates vary with grain size, affecting pore-water chemistry and microbial activity depth profiles.
Mapping acoustic backscatter helps distinguish sediment types linked to Amazon discharge variability over decades.