军队扮演什么角色为了取回轻板下的密集的板块?- 江南体育网页版- - - - -地球科学堆江南电子竞技平台栈交换 最近30从www.hoelymoley.com 2023 - 04 - 01 - t05:55:34z //www.hoelymoley.com/feeds/question/24795 https://creativecommons.org/licenses/by-sa/4.0/rdf //www.hoelymoley.com/q/24795 4 军队扮演什么角色为了取回轻板下的密集的板块? Shyam //www.hoelymoley.com/users/28370 2023 - 01 - 26 t10:43:23z 2023 - 01 - 27 t10:26:22z <一口> < p >我是10 th < /一口>年级的学生,我不太了解地质但我在线学习俯冲。它总是提到密度板被俯冲下较小的密度板。我想知道为什么只有被俯冲的密度板?I know its buoyancy will be less, but still it's floating over the mantle and when it collides with the lesser denser plate why is it the one which gets subducted, or what "forces" play the role here?

//www.hoelymoley.com/questions/24795/-/24799 # 24799 0 答案由沃尔夫冈Bangerth力量扮演什么角色为了取回轻板下的密集的板块? 沃尔夫冈Bangerth //www.hoelymoley.com/users/5259 2023 - 01 - 26 t21:51:50z 2023 - 01 - 26 t21:51:50z < p >确实由于其化学成分,海洋板块(主要由玄武岩)密度比大陆板块(主要有花岗岩组成的)。因此,当大陆和大洋板块,推动相互见面,大洋板块普遍失去了,下面去。< / p > < p >这可以解释为什么俯冲板块最终在大陆,但不是他们为什么实际上保持下沉到地幔。这可能是令人惊讶的起初因为的大洋板块俯冲带是由相同的材料作为地幔(总的来说)。但它比地幔冷,冷通常意味着密度(水/冰是例外)。这是因为俯冲板块一直在数千万年来,表面冷却接触海洋和表面。所以它的密度,因此沉落在周围地幔。我们相信一些俯冲板块下沉到地幔底部之前他们最终达到温度平衡与周围地幔。< / p > //www.hoelymoley.com/questions/24795/-/24801 # 24801 1 回答大卫Hammen力量扮演什么角色为了取回轻板下的密集的板块? 大卫Hammen //www.hoelymoley.com/users/239 2023 - 01 - 27 t10:20:25z 2023 - 01 - 27 t10:26:22z < p >一旦俯冲开始,它会继续因为沉没板把材料。This is "slab pull", which dominates over "ridge push" at a subduction zone. How subduction starts is an open research question. How subduction continues once started is more or less settled science, so this answer focuses on what happens after subduction has started.

The reason the mafic oceanic crust (which is indeed less dense than ultramafic mantle rock) sinks is because at enough depth, the temperature becomes high enough to cook out the portions of the sinking slab with a lower melting point. Basalt and related rock in oceanic crust is a mix of multiple chemicals, some with lower melting points, some with higher melting points. At enough depth, the materials with a lower melting point melts while the materials with a higher melting point remain solid.

The materials with a lower melting point also have a lower density than the materials with a higher melting point. The less dense liquid portion of the partial melt rises through the overlying material to form the volcanic arc oftentimes associated with a subduction zone. This is the key process by which much of the continental crust formed.

What's left behind in the solid portion of the partial melt is dense ultramafic rock, basically the same chemically as mantle material. As melting is endothermic, the partial melting process cools the remaining solid portion even further. (It was already a bit cooler than the surrounding upper mantle.) That makes it even more dense, denser than the surrounding mantle material, and hence it sinks.

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