Observation of manganese deposits in the area of the Galapagos Rift by the ALVIN submersible in 1977

Ranging in height from gentle hills of less than a meter to steep-sided giants of more than 20 m, the mounds of the Galapagos Rift are spectacular hydrothermal features. Their internal temperatures have been measured at up to 13°C above the bottom water temperature, and total heat flow (conducted plus convected) can be several hundred to several thousand times the normal oceanic values. Fluids, when they discharge from the mound, do so at a very slow rate and at temperatures probably quite near the bottom water temperature. The mounds are principally composed of iron silicates intermixed and incrusted with lesser amounts of manganese oxides. They are generally found in rows, in a uniformly sedimented area above faults or fractures in the crustal rocks which permit fluids to escape from a deep hydrothermal aquifer. The sediment blanket in some way alters the chemistry of the ascending thermal fluids and leads to the development of mounds. The mounds field, covering an area of at least 200 km2 and consisting of thousands of individual mounds, is probably less than 300,000 years old; and many of the mounds may be only a few tens of thousands of years old or less.

加拉帕戈斯裂谷（Galapagos Rift）的热液丘体高度跨度极大，从不足1米的缓坡小山，到高达20余米的陡峭巨型丘体，是极具观赏性与科研价值的热液地貌（hydrothermal features）。其内部温度经测量最高较底层海水温度高出13℃，总热流（传导热流与对流热流之和）可达常规大洋热流基准值的数百至数千倍。当流体从丘体中喷溢时，流速极为缓慢，其温度大概率接近底层海水温度。该类丘体主要由铁硅酸盐（iron silicates）构成，并混杂、包裹有少量氧化锰（manganese oxides）。它们通常呈条带状分布于地壳岩石（crustal rocks）断层或裂隙上方的均匀沉积区域，这些构造为流体从深部热液含水层（hydrothermal aquifer）逸出提供了通路。沉积层以特定机制改变了上升热液的化学组成，进而驱动了热液丘体的形成。这片丘体群分布面积至少达200平方千米，包含数千个独立丘体，其形成年代推测不足30万年；其中多数丘体的年龄仅为数万年甚至更短。