Unit 3 汉译英

汉译英：

我们生活的地球是一个形状像梨一样的椭球体（The Earth we live on is a pear-shaped ellipsoid），它的赤道半径6378 km，极半径6357 km，平均地球半径6371 km，总质量5.976×1024 kg（with an equatorial radius of 6378 km，a polar radius of 6357 km，an average radius of 6371 km and a total mass（quality）of 5.976×1024 kg）。地球由三大圈层组成，分别为地壳、地幔和地核（The Earth is composed of three layers，namely，the crust，the mantle and the core）。地壳是最外部，也是最薄的圈层（The crust is the outermost and the thinnest layer），平均厚度是大陆从地表到地下35 km，海洋从洋底到地下7 km（with an average thickness of 35 km from the surface of continent to ground and of 7 km from the ocean bed to ground）。地壳上部主要为花岗岩，下部主要为玄武岩（The upper crust is composed mainly of granite and the lower crust is composed mainly of basalt）。莫霍界面把地壳和地幔分开，以上为地壳，以下为地幔（The interface separating the crust from the mantle is the Moho interface，above which is the crust and below which is the mantle）。莫霍界面两侧波速和物质密度都有变化，物质也发生化学变化，因此，莫霍界面是一个化学间断面（The velocity and density of matter has changed, and matter chemical changes have taken place over the Moho interface, therefore, the Moho interface is a chemical discontinuity）。地幔分为上地幔和下地幔（The mantle can be divided into the upper mantle and the lower mantle）。上地幔从地下35 km到670 km（The upper mantle exists from a depth of 35 km to a depth of 670 km below the surface），上地幔的物质主要为橄榄岩和榴辉岩，以及玄武岩岩浆（The upper mantle is composed mainly of olivine, eclogite and basaltic magma），地球上火山喷发出的大规模玄武岩岩浆主要来自上地幔（Massive basaltic magma resulting from volcanic eruption on the Earth is mainly from the upper mantle）。在上地幔还有分布在全球范围的410 km间断面和600 km间断面（There also has worldwide discontinuities with a depth of 410 km and 600 km in the upper mantle）。上地幔的温度大约1000℃，压强从1.1 GPa到23.8 GPa（The temperature of the upper mantle is about 1000℃and the pressure is from 1.1 GPa to 23.8 GPa）。下地幔从670 km一直延伸到2891 km的核幔边界（CMB）（The lower mantle exists from a depth of 670 km to the CMB(the Core and the Mantle Boundary) with a depth of 2891 km）。下地幔的主要物质组成为Mg（32%）、FeO （18%）、SiO2（50%）（The lower mantle is composed mainly of Mg（32%）、FeO（18%）、SiO2（50%）），下地幔处于高温高压状态，温度约为3700℃。压强从23.8 GPa增大到135.7 GPa（The lower mantle is at a high temperature and pressure condition and the temperature is about 3700℃and the pressure is from 23.8 GPa to 135.7 GPa）。

The Earth we live on is a pear-shaped ellipsoid with an equatorial radius of 6378 km，a polar radius of 6357 km，an average radius of 6371 km and a total mass of 5.976×1024 kg. The Earth is composed of three layers，namely，the crust，the mantle and the core. The crust is the outermost and the thinnest layer with an average thickness of 35 km from the surface of continent to ground and of 7 km from the ocean bed to ground. The upper crust is composed mainly of granite and the lower crust is composed mainly of basalt. The interface separating the crust from the mantle is the Moho interface，above which is the crust and below which is the mantle. The velocity and density of matter has changed, and matter chemical changes have taken place over the Moho interface, therefore, the Moho interface is a chemical discontinuity. The mantle can be divided into the upper mantle and the lower