Earth’s middle layer may be squishier than previously thought.
A new study suggests the intense heat and pressure deep in the Earth makes sound waves travel more slowly through parts of the lower mantle than had been previously estimated, suggesting that part of this layer of the inner Earth is softer than expected.
Below the crust of the Earth (the layer we stand on) lies the viscous mantle. The lower portion of the mantle lies below the more rigid upper mantle and above the liquid outer core. It extends from about 400 to 1,800 miles (660 to 2,900 kilometers) below the surface.
Temperatures and pressures at this depth are so brutal that they can change the materials there into states that don't exist on Earth's surface. Pressures can reach 230,000 times the pressure at sea level and temperatures range from 2,800 to 6,700 degrees Fahrenheit (1,500 to 3,700 Celsius).
These forces change the configurations of electrons in the mineral ferropericlase in the lower mantle, making it "softer" than previously estimated.
The study, by Alexander Goncharov of the Carnegie Institution’s Geophysical Laboratory and colleagues, is detailed in the Jan. 25 issue of the journal Science.
译文:
地球“心太软”
地球的中间层可能比之前预想的更湿、更软。
一项新的研究表示在地球深处极高的热度和极大的压力使得音波通过下地幔传播的速度比之前估计的更慢，表示地球内部该层的部分比预期的更软。
在粘粘的地幔上那坚硬的地球外壳之下（我们站立的层面）。该地幔较低的部分在更硬的上地幔之下，并在液体外核之上。它从地球表面下约400到1800英里（660到2900公里）处延伸出来。
这个深度的温度和压力是非常严苛的，他们可以将材料变成不存在于地球的表面的状态。压力可以达到在海平面上压力的23万倍，温度从2800到6700华氏温度（1500到3700摄氏温度）。
这些力量改变了在低地幔中矿石低铁黑硬绿泥石中电子的结构，使其比之前估计的更“软”。
卡内基研究所地球物理学实验室的Alexander Goncharov和他的同事们进行的此次研究内容详细刊登在1月25日发行的《科学》杂志上。