[揽瓜阁精读] 82.Lava

YannTse1111

P1

-地幔温度很高，科学家猜测1960年ocean crust出现，很多石头融化成液体。

-只有有一点压力释放地幔石头就会融化。

-但是很难解释石头怎么融化然后喷发到地球表面。

-Melt密度比地幔石头低，所以会被抬升到压力更小的地方。

-But实验显示melt的化学成分和从海里搜集到的样本不一样。

-实验发现melt的化学成分会根据形成深度各有不同。。

-melt抬升会释放很多矿物质，比如orthopyroxene

-科学家推测抬升的越高，orthopyroxene分解越多，会产生更多olivene。

-把实验结果和海底样本对照，发现样本里的melt都在超过45km的深度形成。

-这个结论质疑了melt是怎么能在这么深的地方还能维持成分不变。

P2

-1970年科学家给出答案：melt是从一个大裂谷升上去的，升的快所以来不及和其他物质发生反应。

-科学家认为浮力使得melt把石头都撞碎了，原理类似破冰船。

-N发现大裂谷有种不常见的O石头。

-O在地幔上层，板块运动相撞的时候会喷发到地球表面。

-举例：A和E板块运动，N发现一种叫做dikes的纹路，认为是melt结晶的裂缝。

-问题在于dikes上面找的melt和45km对不上。

-而且破冰船理论也未必适用，10km以下的地方更类似于液体，没法撞碎。

P3

-作者尝试解释谜团，着眼另一个假设。

-认为上升的mantle分解orthopyroxene，形成少量olivene。

-计算显示分解过程会扩大空间，形成更大的pores形成可流动的小通道。

-pores增加形成聚合体，小分支汇聚成大通道。

-作者的模型显示90%的melt都聚集在10%的区域。

-所以melt流动的很慢，即使通道很宽，而且有地幔石头堵塞通道。

-经过很长时间melt才经过通道，orthopyroxene都分解完了，剩下少数olivene。

-所以解释了melt的深度。

YannTse1111

P1

-地幔温度很高，科学家猜测1960年ocean crust出现，很多石头融化成液体。

-只有有一点压力释放地幔石头就会融化。

-但是很难解释石头怎么融化然后喷发到地球表面。

-Melt密度比地幔石头低，所以会被抬升到压力更小的地方。

-But实验显示melt的化学成分和从海里搜集到的样本不一样。

-实验发现melt的化学成分会根据形成深度各有不同。。

-melt抬升会释放很多矿物质，比如orthopyroxene

-科学家推测抬升的越高，orthopyroxene分解越多，会产生更多olivene。

-把实验结果和海底样本对照，发现样本里的melt都在超过45km的深度形成。

-这个结论质疑了melt是怎么能在这么深的地方还能维持成分不变。

P2

-1970年科学家给出答案：melt是从一个大裂谷升上去的，升的快所以来不及和其他物质发生反应。

-科学家认为浮力使得melt把石头都撞碎了，原理类似破冰船。

-N发现大裂谷有种不常见的O石头。

-O在地幔上层，板块运动相撞的时候会喷发到地球表面。

-举例：A和E板块运动，N发现一种叫做dikes的纹路，认为是melt结晶的裂缝。

-问题在于dikes上面找的melt和45km对不上。

-而且破冰船理论也未必适用，10km以下的地方更类似于液体，没法撞碎。

P3

-作者尝试解释谜团，着眼另一个假设。

-认为上升的mantle分解orthopyroxene，形成少量olivene。

-计算显示分解过程会扩大空间，形成更大的pores形成可流动的小通道。

-pores增加形成聚合体，小分支汇聚成大通道。

-作者的模型显示90%的melt都聚集在10%的区域。

-所以melt流动的很慢，即使通道很宽，而且有地幔石头堵塞通道。

-经过很长时间melt才经过通道，orthopyroxene都分解完了，剩下少数olivene。

-所以解释了melt的深度。

xixio

x.w 发表于 2022-8-21 11:39
看一下！

同意！               

xixio

82----探究lava transport的真相
生词：
Researchers hypothesize that ocean crust originates as melt (liquid rock)
Release of pressure--->melt to form deep within the mantle rock
// explain how the rock sweat gets to the surface is difficult: melt is less dense so it will migrate upward, but the chemical composition of melt did not seem to match up with the composition of rock samples---chemical composition of melt in the mantle varies depending on depth, and the composition is controlled by an exchange between the melt and the minerals that it passes through----as melt rises, it dissolves ortho and leaves behind olivine
==>infer: the higher the melt form, the more ortho is would dissolve, and more olivine would be left

Lava samples: all of the melt formed at depths greater than 45km, without dissolving any ortho from the surround rocks---->how they rise while preserving the composition?

In 1970s, scientists proposed an answer: the melt take the last journey along enormous cracks.
Cracks would allow the melt to rise so rapidly that it would have no time to interact with the surrounding rock
Some suggested: the buoyant force of migrating melt be enough to fracture the solid rock above + 类比
AN discovered evidences for such cracks while examined unusual rock formation called ophiolites:（when oceanic crust gets old and cold and become so dense that it sinks back into the mantle—subduction zones; and ophiolites are thick sections of old seafloor解释什么是ophiolites + example）----they found unusual light-colored veins called dikes---melt cracks
// the problem is that the dikes are filled with rock that crystallized from a melt + the icebreaker scenario may not work well

To explain the ongoing mystery: alternative hypothesis
Chemical theory: as rising melt dissolves ortho crystals, it precipitates a smaller amount of olivine
Dissolution process: as the pores grow, they connect to form elongate channels (类比), and they suggested that more than 90% of the melt is concentrated into less than 10% of the area,-->channel 100 meters or more wide, and many crystals of the mantle rock remain intact, congesting and inhibiting the movement of the fluid--->so the melt flows slowly; over time, so much melt passes through the channels that all the soluble ortho crystals dissolve away, leaving only crystals of olivine (unable to dissolve) --->the composition of the melt can no longer adjust to decreasing pressure and instead records the depth at which it last saw an ortho crystals.
One of the most important implication---focused porous flow---only the melt at the edges of channels dissolves ortho; melt within the inner part can rise unadulterated无杂质的

薯片家的

P1：背景
学者假设海洋地壳来源于液体岩石melt，后面讲机制
即使小小压力都能让melt在深层地幔岩上形成微观细孔，但是melt怎么到表面的呢？因为melt是想去压力小的地方，但是实验表明melt又没有这些属性---又发现不同深度化学属性上的melt还不一样，因为化学属性是由melt和所在深度的岩石分子融合而成，有人说可以根据melt推测地幔的深度，但中海脊又有证据说并不能

P2：递进
melt只能记录最后它无法流动的时间

P3：递进
melt推动底下岩石向上活动，以至于板块碰撞，但在中海脊的情况不是

feijinbufeijin

1. Mentioned one hypothesis: ocean crust originates as tiny amount of liquid rock known as melt. The difficult part is to explain how the rock sweat gets to the surface. Density of melt is lower than the mantle rocks— melt will migrate upward—the composition test in laboratory can't prove it—almost all the lava has composation from 46km depth mantle— how the melt to upward without dissolving any O from the surrounding rock
2. Owner's working on above mystery. Explaining the reason why melt is getting larger and why the melt flows slowly
Explain how ocean crust forms and correct a misunderstanding previous point of where the melt formed.

Austin_001

看一下！               

吾铜wt

马一下

吾铜wt

p1:
bg: ocean crust starts from little amout liquid rock.
topic: explaining how the rock sweat gets to the surface.
first hypothesis: melt is less dense, so it constantly migrate upward. But the chemical composition doesn't match up with mid-ocean sample.
the flaw of first hypothesis: experiment showed the chemical composition of orth and oliv will change while melt rised. →debate→ question: yet the composition of most mid-ocean samples is different than what scientist thought.
p2: a 1970s explaination
second hypothesis: the melt must make the last leg of its upward journey along enormous cracks. open crack let melt rise fast so they don't exchange orth, and there is enough pressure for melt to facture the solid rock above like an icebreaker.
one group of scientists found evidence.
flaws: scientists used disk to explain theory. but disks are filled with the rocks from a melt and it is on a higher places. And icebreaker scenario doesn't fit.

p3: author's explaination in late 1980s
third hypnothesis:
geo pattern: as rising melt dissolves orth crystals, it precipitates a smaller amout of oliv, resulting in a greater volume of melt. → This dissolution enlarge open spaces, creating larger pores, giving melt better way to flow.  →pores grow, elongate channels, then larger channels. → space is small so they flow slowly.
explain chemical: orth is dissovled, only oliv and others. So melt can't decrease pressure, and it records the depth of none-orth level.
implication: only the melt at the edges dissolves orth from the surrouding rock.
好难的一篇，看得我绝望。。

哈哈隔mm

结构：
P1:提出一个问题
P2:回答问题
P3:拥有答案

段落大意：
第一段：
--假设：海洋地壳来源于一种融化的液体岩石（原理就是melt可以比它形成的岩石密度更低，所以能往高处走，直到低压地区）
--问题：但是发现melt的组成部分和中部屋脊的不一样（原因是melt的组成部分取决于它形成的深度，组成部分是由melt和岩石穿过的矿物质之间的离子转换形成的）
--发现：melt会溶解or矿物质，降解另一种矿物质ol
--推断：越高的melt形成，溶解的or越多，降解的ol越多
--问题：但是中部屋脊的岩浆的组成成分很丰富，说明melt在没有溶解or的情况下达到了45km上方，是如何形成的呢？
第二段：
--运用另一种假设在论文中解释p1问题
--发现1.melt在溶解or过程中会扩大自身体积，最终扩大海洋空间用以穿过，形成更大的管道 2. 90%的melt会凝聚到小于10%的区域里面，即使是在最宽的管道里面，melt还是喜欢紧挨在一起，使得通道变得拥挤，其他的液体无法通过
--结果：最终melt一年只能移动一点点，溶解了大部分or，只留下了一部分ol和无法溶解的其他矿物质，继而melt无法继续在低压地区上行，停留在能看见or晶体的深度，melt只在通道的边缘溶解来自于周围地区的岩石，内部的melt则可以上升
第三段：
--科学家们后来发现melt可以引起岩石碎裂，碎裂过程允许melt快速上升
--案例：SO位置上，两大板块的碰撞使得裂纹产生，melt可以在达到海底之前结晶，唯一的问题就是充满了在地狱45km深度处形成的melt的岩石
--但是这个场景并不适用于低于10km处的中部屋脊，此处无法轻易形成裂纹