Earth structure.
地球结构。
Earth is like a very big solid ball.
地球就像一个非常大的实心球。
From its top to its center, Earth is about 6,000 kilometers in depth.
从顶部到中心，地球大约有6000公里深。
Earth has three layers, the crust, the mantle, and the core.
地球有三层，地壳、地幔和地核。
The crust is about 5 to 70 kilometers in depth and is solid rock.
地壳大约有5到70公里深，是坚硬的岩石。
Mantles live on masses of land called continents.
曼特生活在被称为大陆的大片陆地上。
There are seven continents.
有七大洲。
They are part of the crust.
它们是地壳的一部分。
Below the crust is the mantle, which is made of rock.
地壳下面是地幔，由岩石构成。
It is about 3,000 kilometers in depth.
深度约3000公里。
The mantle is so hot that some of the rock is liquid.
地幔很热，以至于有些岩石是液体。
The crust is above the mantle and floats on it.
地壳在地幔上面，漂浮在上面。
The continents move very, very slowly.
大陆的移动非常非常缓慢。
Below the mantle is the core.
地幔下面是地核。
It is about 3,000 kilometers in depth.
深度约3000公里。
The core is the hottest layer.
核心是最热的层。
It is made of metal, some of which has melted.
它是由金属制成的，其中一些已经熔化了。