翻译英语句子

Studies (主语) of the gravity field （定语，修饰主语）of the Earth（定语，修饰前面的of 短语） indicate（谓语动词） that （引出宾语从句）its crust and mantle（宾语从句中的主语） yield（宾语从句中的谓语动词） when（引出时间状语从句，做宾语从句中的时间状语从句） unusual weight（状语从句中的主语） is placed（状语从句中谓语） on them（状语从句中做谓语动词词组的状语）.

翻译：地球的引力场研究指出当异常重量施加在地球表层和外壳之上时，他们会发生塌陷。

英文地球由什么构成

地球或其它行星由于某种原因而带上了电荷或者导致各个圈层间电荷分布不均匀。这些电荷由于随行星的自转而做圆周运动，由于运动的电荷就是电流，电流必然产生磁场。地球磁场（theearthmagneticfield）是地球周围空间分布的磁场。它的磁南极大致指向地理北极附近，磁北极大致指向地理南极附近。磁力线分布特点是赤道附近磁场的方向是水平的，两极附近则与地表垂直。赤道处磁场最弱，两极最强。地球表面的磁场受到各种因素的影响而随时间发生变化。

Earth?is?unique?among?the?known?planets:?it?has?an?abundance?of?water.?Other?worlds?—?including?a?few?moons?—?have?atmospheres,?ice,?and?even?oceans,?but?only?Earth?has?the?right?combination?to?sustain?life.

Earth's?oceans?cover?about?70?percent?of?the?planet's?surface?with?an?average?depth?of?2.5?miles?(4?kilometers).?Fresh?water?exists?in?liquid?form?in?lakes?and?rivers?and?as?water?vapor?in?the?atmosphere,?which?causes?much?of?Earth's?weather.

Crust

Earth's?crust?is?made?up?of?several?elements:?iron,?32?percent;?oxygen,?30?percent;?silicon,?15?percent;?magnesium,?14?percent;?sulfur,?3?percent;?nickel,?2?percent;?and?trace?amounts?of?calcium,?aluminum?and?other?elements.

The?crust?is?divided?into?huge?plates?that?float?on?the?mantle,?the?next?layer.?The?plates?are?constantly?in?motion;?they?move?at?about?the?same?rate?as?fingernails?grow.?Earthquakes?occur?when?these?plates?grind?against?each?other.?Mountains?form?when?the?plates?collide?and?deep?trenches?form?when?one?plate?slides?under?another?plate.?Plate?tectonics?is?the?theory?explaining?the?motion?of?these?plates.

Mantle

The?mantle?under?the?crust?is?about?1,800?miles?deep?(2,890?km).?It?is?composed?mostly?of?silicate?rocks?rich?in?magnesium?and?iron.?Intense?heat?causes?the?rocks?to?rise.?They?then?cool?and?sink?back?down?to?the?core.?This?convection?—?like?a?lava?lamp?—?is?believed?to?be?what?causes?the?tectonic?plates?to?move.?When?the?mantle?pushes?through?the?crust,?volcanoes?erupt.

Core

At?the?center?of?the?Earth?is?the?core,?which?has?two?parts.?The?solid,?inner?core?of?iron?has?a?radius?of?about?760?miles?(about?1,220?km).?It?is?surrounded?by?a?liquid,?outer?core?composed?of?a?nickel-iron?alloy.?It?is?about?1,355?miles?(2,180?km)?thick.?The?inner?core?spins?at?a?different?speed?than?the?rest?of?the?planet.?This?is?thought?to?cause?Earth's?magnetic?field.?When?charged?particles?from?the?solar?wind?collide?with?air?molecules?above?Earth's?magnetic?poles,?it?causes?the?air?molecules?to?glow,?causing?the?auroras?—?the?northern?and?southern?lights.?

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