求英语大侠帮忙翻译The Earth comprises three principal layers : the de

求英语大侠帮忙翻译
The Earth comprises three principal layers : the dense , iron-rich core , the mantle made
of silicate rocks that are semi-molten at depth , and the thin , solid-surface crust .There
are two kinds of crust , a lower and denser oceanic crust and an upper , lighter continental
crust found over only about 40 percent of the Earth’s surface . The rocks of the crust are
of very different ages . Some continental rocks are over 3,000 million years old , while
those of the ocean floor are less than 200 million years old . The crusts and the top ,
solid part of the mantle , totaling about 70 to 100 kilometers in thickness , at present
appear to consist of about 15 rigid plates , 7 of which are very large . These plates move
over the semi-molten lower mantle to produce all of the major topographical features
of the Earth . Active zones where intense deformation occurs are confined to the
narrow , interconnecting boundaries of contact of the plates .
There are three main types of zones of contact : spreading contacts where plates
move apart , converging contacts where plates move towards each other , and transform
contacts where plates slide past each other . New oceanic crust is formed along one or
more margins of each plate by material issuing from deeper layers of the Earth’s
crust , for example , by volcanic eruptions of lava at mid-ocean ridges . If at such
a spreading contact the two plates support continents , a rift is formed that will
gradually widen and become flooded by the sea . The Atlantic Ocean formed like
this as the American and Afro-European plates moved in opposite directions . At the
same time at margins of converging plates , the oceanic crust is being reabsorbed
by being subducted into the mantle and remelted beneath the ocean trenches .When
two plates carrying continents collide , the continental blocks , too light to be
drawn down , continue to float and therefore buckle to form a mountain chain along
the length of the margin of the plates .

地球包括三个主要层次：稠密,富含铁的核心,提出了地幔
硅酸盐岩石是半熔化深度,以及薄,固体表面的地壳.有
两种地壳密度较低和大洋地壳和上,更轻大陆
地壳发现了大约只有百分之四十的地球表面.岩石的地壳
非常不同年龄.一些大陆岩石超过3000亿岁,而
这些洋底是不到200万年.结壳和顶端,
固体部分的地幔,总计约70至100公里的厚度,目前
似乎包括约15刚性板,其中7个是非常大的.这些板块移动
在半熔化的地幔降低生产所有主要的地形特征
地球.活跃的地区发生激烈的变形局限于
狭隘的,互相联系的边界板块.
主要有三种类型区的联系：在板接触传播
除了移动,融合的情况下接触板朝向对方,并把
接触板滑过去在对方.新的大洋地壳形成沿一个或
更多的利润每块板的材料签发从更深层次的地球
地壳,例如火山喷发的熔岩在洋中脊.如果在这种
1蔓延联系两大板块支持大陆的分裂,将形成
逐步扩大,并成为淹没大海.在大西洋形成的像
这是美国和非裔欧洲板块走势相反.在
同时在板块边缘的融合,在大洋地壳正在吸收
被俯冲到地幔和重熔在海洋壕沟.当
两大板块碰撞进行大陆,大陆块,过轻的
被取用,继续浮动,因此扣形成山脉沿
长度缘板块.