[揽瓜阁精读] 252. 岩石Sweating

duckblue0228

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苏二在努力

P1 1799, AH found granite boulders near OR
•        Smooth, black, and as if coated with plumbago.
•        Indian legend: rocks have been burnt by the tropical sun.
P2 boulders have generated scientific mystery for two centuries.
•        CD found rocks in BB. Others found in rainforests, underneath glaciers.
•        Hypothesis:
Deposits left by the ancient ocean, residues from decomposing organic matter
Most popular hypothesis: Rock sweating
But: was the sun hot enough?
P3 physical and chemical structure of rock varnish
•        Recent scientific name: rock varnish
•        While the origin of rock varnish is enigmatic, structure become understood
A thin layer on the rock’s surface
60% clay minerals, 20-30% oxide, more than 30 minor compounds
Amount of manganese determines the color of varnish.
Black: manganese levels up to 100 times
Brown orange: lacks manganese, abundant iron oxides. Appear in the bottom of rock and inside the rock
In Peru desert, manganese is intermediate, brownish orange
P4 1981, TMO and I suggested that bacteria concentrate manganese in rock varnish
•        First: manganese-rich varnish often forms where water flows rocks. Moisture=>microrganism
•        Second: varnish develop well on the porous surface where easily flushed and poor in nutrients. Oxidizng mixotrophs able to live, heterophic organisms unable to live
P5 third observation: dark varnish grows on rocks with a nearly neutral PH
•        Mg-O operates in alkaline environment, where ph>9 => plausible candidates
•        Local ph too high => organe
P6 there are many documented interactions between clay and bacteria
•        Clay particles absorb onto the surface of bacteria
•        Clay concentrate neutrients,
P7 Examination: the presence of bacteria
•        Found Mg-concentrating bacteria
•        Produce similar bacteria

taylor_2008

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echoooo3333

252：
1.        VON发现了（black、coating、rock、boulder）。印度人说他的来源。Crew嘲笑
2.        有关于来源的假设和最可能的假设——sweating：水蒸发，precipitation变成black在表面：但有一个问题，hot sun够用吗？
3.        Rock vanish：起源迷惑但是物理化学性质ok m氧决定黑色，iron氧气橙色：底层和裂缝crevice的rock很常见
4.        决定性证据：生物one 细菌集中在rock，基于证据1）水（提供环境）2）在xx表面（harsh环境：m ok）3）中性PH值（可对比橘色的）（非生物的m是在碱性）
6        Clay保护细菌，细菌生成M——因此去证明细菌（成功！）

Plumbago石墨 scoff嘲笑 boulder巨石=rock  apex=peak=summit定点
deposit沉积物=sediment=precipitation沉淀析出降水 enigmatic神秘的 millimeter毫米 zinc锌 copper铜 manganese锰 crevice裂缝 circumstance条件情况 circumstantial 依照情况的、偶然的：circumstantial evidence间接证据 concentrate集中、浓缩 metabolism新陈代谢

Manss

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Ak777

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Shining-Cindy

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ivanahhh

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一色彩羽ove

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pinx

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