@ Rich Angel Rocks are EVERYWHERE! Even above your head… OUT IN SPACE!! 的回答
According to the Big Impact Theory, also called the Big Splash Theory, a Mars-sized planet which we now refer to as Theia crossed paths with the early Earth. This was soon after the formation of the solar system. Earth’s history is broken into discreet periods of time and named in a way that is descriptive of the ruling conditions. Those days of the young Earth were called the Hadean Eon because it was very Hell-like, with oceans of magma (lava-hot liquid rock).
根据“大撞击理论”（也称为“大飞溅理论”），一个被称为“Theia”的火星大小的星球，飞向了地球 这是太阳系形成后不久。 地球的历史分为不连续的时期，并以描述统治条件的方式命名。 年轻时的地球被称为Hadean Eon，因为它非常类似于地狱，充满了岩浆（熔岩热的液态岩石）海洋。
When the two planets met, it was likely at a glancing angle, not a direct head-on collision. It gouged out a large divot of Earth, much of which fell back to the surface. Some of this material was blasted loose with so much energy, it stayed in orbit around Earth, forming a cloud of glowing hot material that eventually coalesced onto larger, and fewer bodies until the only thing that orbited the Earth was a single large moon.
当两个行星相遇并相撞，但它们可能只是以某一个角度相撞，而不是直接的正面碰撞。 它撞走了一块大片的地球，其中许多掉回了地面。 这些物质中的一些被巨大的能量炸散，它停留在绕地球运行的轨道上，形成一团炽热的热物质，最终聚结到更大，数量更少的物体上，知道绕地球轨道运行的只是单个月球了。
If you were to ask me to show you the hole where Theia made its Big Splash, I wouldn’t be able to comply. Earth is too geologically active and all traces of that long-ago impact would have been erased many times over by now. I can tell you this, though. The Earth is made up of layers. There’s the outer layer of rock called the crust, then a hot, more plastic layer called the mantle and finally a core made up of nickel-iron, itself divided into a liquid outer core and a solid inner core.
如果您要我向您展示Theia撞出的那个洞，那我没办法。 地球在地质上过于活跃，到现在为止，这种长久影响的所有痕迹已经被抹掉了很多次。 我可以告诉你。 地球是由地层组成的。 岩石的外层称为地壳，然后是较热的易流动的层，称为地幔，最后是由镍铁制成的岩心，其本身分为液态外层岩心和固态内层岩心。
Over time, heavy, or more accurately, higher density materials (like much of Earth’s iron) has plunged into the interior while the material left to “float” on the Earth’s surface is the lighter or less dense material. My point is that the Earth has kneaded itself into layers of progressively more dense stuff as you go down. If the moon were made up of an equal proportion of these layers, it’s overall density would be much like the overall density of the Earth… BUT IT’S NOT!
随着时间的流逝，重物质，或更准确地说是高密度的物质，（像地球上的大铁一样）掉入了内部，而留在地球表面上“漂浮”的物质则是较轻或密度较小。 我的意思是，当您从外太空往地球中心前进时，你遇到的物质密度越来越高。 如果月亮由这些层的组成，那么它的总体密度将与地球的总体密度非常相似……但事实并非如此！
Earth’s average density is about 5.5 grams per cubic centimeter while the moon’s density is about 3.3 g/cm^3. That tells us that the stuff that makes up the moon is only scooped out of the material of the Earth’s outer mantle where the density is about 3.4 g/cm^3. So, without being able to pin-point a “where” on the map, I can show you from how deep Theia blasted stuff out of the Earth.
地球的平均密度约为每立方厘米5.5克，而月球的密度约为3.3克/立方厘米。 这告诉我们，构成月球的东西只是从密度约为3.4 g / 立方厘米的地球外地幔的材料中逃出的。 因此，在无法精确定位地图上的“位置”的情况下，我只能告诉您Theia炸开地球的深度。
Incidentally, the impact is also being credited for shifting our axis of rotation to its present 23ish degrees. Maintaining that angle of inclination has been attributed to the stabilizing effects of our large moon’s gravity. It is this shifted axis that gives Earth its seasons, and the persistence of the inclination that keeps our climate more stable than it would otherwise be.
顺便说一下，地轴偏移到目前的23ish度也归功于这次撞击。 保持该倾斜角度归因于我们的大卫星重力的稳定作用。 正是这条偏移的轴使地球有了自己的季节，并且倾斜的持久性使我们的气候比以前更稳定。
Our “next-door neighbor”, the planet Mars has a similar axial inclination but Mars lacks a single large moon like the one we have so, its tilt-angle is thought to drift or wander over time causing havoc with its climate. Perhaps that particularly bad day amid such a hellish period was, in part, responsible for making our world so friendly to life.
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You may enjoy my responses to other cool Quora questions, like the one David asked: Rich Angel’s answer to What materials are there on Mars that are of value to Earth? .
您可能会喜欢我对Quora其他一些很酷的问题的回答，例如David所问的：Rich Angel对火星上存在的对地球有价值的材料的回答？ 。
Cheers, and Ad Astra!
This seems to make the Earth Moon system remarkably unique, maybe greatly reducing the chances of finding another like it…
If the universe weren’t so vast, I would be tempted to say our little world is one-of-a-kind. The string of unlikely circumstances that contribute to making our home world so “homey” is astronomical. But so is the rest of creation. Thanks for contributing.
如果宇宙没有那么广阔，我会很想说我们的小世界是独一无二的。 一系列使我们的家庭变得如此“温馨”的事件概率实在太小了。 但是其余的创造事件也是如此。 感谢您的贡献。
I always wondered if it was partly the Big Smash that caused the tectonic plates.
We know that Mars and Venus don’t have the same level of tectonic plate activity, but I have never seen an explanation as to why we have it and other planets don’t.
It is like the Earth’s crust got smashed, but ended up stuck to the mantle just like how a hard boiled egg shell can “crack” when you bang it but a lot of the pieces remain stuck to that thin skin between the cooked white and the shell.
So the Earth’s tectonic motion depends on internal heat but it also depends on a couple other facilitators. For example our world is a wet one. I once heard a joke that sums up the matter: They should have named our world, “Ocean” because 3/4 of the surface is covered with water. That water facilitates the motion by lubricating faults. NO JOKE.
因此，地球的构造运动取决于内部热量，但也取决于其他几个促进因素。 例如，我们的世界是一个潮湿的世界。 我曾经听过一个笑话来概括这个问题：他们应该将我们的世界命名为“海洋”，因为3/4的表面都被水覆盖。 该水通过润滑作用来促进运动。 不是开玩笑。
Then there’s the matter of crust. There’s two kinds. The kind that continents are made up from, and the kind that makes up the ocean floor. Continental crust has an average density of 2.83 g/cm^3, while the mid-ocean ridge basalts (MORB’S… again, no joke) has an average density of 2.90 g/cm^3. This 7/100th’s of a gram difference in density is enough to let some cool stuff happen. The lighter continental crust floats on top of the mantle (3.3 g/cm^3) while the oceanic crust will only do so while it is hot. The hottest MORB’s are closest to their place of origin, at the mid-ocean ridges, while the coolest borders the continents. Some of these borders have subduction zones, where the oceanic crust actually breaks and dives under other crust.
然后是地壳的问题。 有两种。 大陆组成的种类，以及构成海底的种类。 大陆壳的平均密度为2.83 g / cm ^ 3，而中洋脊玄武岩（ mid-ocean ridge basalts ，MORB’S…，又不是笑话）的平均密度为2.90 g / cm ^ 3。 这0.07克的密度差足以让一些酷的事情发生。 较轻的大陆壳漂浮在地幔顶部（3.3 g / cm ^ 3），而海洋壳则只有在变热时才会漂浮。 最热的MORB位于海洋中部海脊，是最接近原产地的地方，而最凉爽的则是各大洲的边界。 这些边界中的一些边界具有俯冲带，实际上，洋壳在该俯冲带破裂并在其他地壳之下俯冲。
When you imagine the planet cut in cross-section, you will see that there are several places where this cold ocean crust subduction is going on. It is typically coupled with areas of volcanism on the overriding plate. Think about the chain of volcanoes along the US Pacific North-West. Just off-shore, the Juan de Fuca plate is diving under North America. The ocean floor acts as a conveyor belt that comes up at the mid-ocean ridge and plunges at the subduction zones. The continents act like items being moved around by this conveyor (the analogy is not perfect as the continents rest mostly on the mantle and not directly on top of ocean basalt… just adjacent to it).
当您想象这颗行星的横截面切开时，您会发现冰冷的洋壳俯冲正在发生的多个地方。 它通常与覆盖板上的火山区域相结合。 考虑一下美国太平洋西北部的火山链。 就在海上，Juan de Fuca板块正在北美洲潜水。 海床起着一条输送带的作用，它上升到大洋中脊，并在俯冲带俯冲。 各大洲的行为就像是通过传送带在周围移动的物品（类比并不完美，因为各大洲主要位于地幔上，而不是直接位于海底玄武岩之上……而是紧邻其）。
Now there is one other factor I have to mention. Have you seen those little hand-held puzzles that have space for 9 square tiles in a 3×3 configuration? It’s sort of a flat-earther’s rubics cube. Notice that there are only 8 tiles. The ninth tile is gone and there is an empty space or gap. You are able to move any tile adjacent to the gap into the gap, thereby opening a gap elsewhere on the tile board.
现在，我不得不提到另一个因素。 您是否看到过一些小型拼图游戏，它们以3×3的配置可以放置9个正方形的瓷砖？ 这有点像地球平面上的魔法。 请注意，只有8个图块。 第九个图块不见了，有一个空白或缝隙。 您可以将任何与该间隙相邻的图块移动到该间隙中，从而在图块板上的其他位置打开一个间隙。
You can move the tiles around until you get them in the correct order to make a picture or whatever. The key is the missing tile. Earth’s surface is only covered by about 25% of continental crust which does not sink into the mantle. The balance is this thin oceanic basalt crust that readily sinks to strategically make room for the continents to move. Between this space solution, plenty of heat to churn it all up, and plenty of water to lubricate the motion, plate tectonics is a lead-pipe cinch… which is to say, “so easy, it’s a given”.
您可以四处移动图块，直到以正确的顺序将它们排列成图片或其他为止。 关键的是缺少的图块。 地球表面仅被约25％的地壳覆盖，而该地壳没有下陷。 两者之间的平衡是这种薄薄的海洋玄武岩地壳，很容易下沉，为各大洲移动提供了空间。 在这种太空解决方案之间，有大量的热量将其搅动起来，还有大量的水来润滑运动，板块构造就像是铅管束带……这就是说，“如此简单，这是既定的”。
Mars… Venus… No water. No planet-wide tectonic behavior. Who knows, maybe no (or, not enough) “oceanic crust”. That leaves volcanoes to carry the burden of transmitting heat from the interior of those worlds since convection cannot reach the surface otherwise.
火星……金星……没有水。 没有全球范围内的构造行为。 谁知道呢，也许没有（或不够）“海洋壳”。 由于对流无法到达地表，火山担起了把星球内部的热量向外传递的重担。
I hope this long-winded breakdown helps unpack the mystery a bit. Thanks for reading and please continue to make comments.