🌍 地壳：我们脚下的薄壳🌍 Earth's Crust: the Thin Shell Under Our Feet

查完人群的疾病，🩺 小医生把放大镜交棒给 🌍 蓝色星球向导：低头看看脚下吧——我们盖楼、种地、奔跑的地面，只是地球表面一层薄得离谱的壳。 Done with diseases of crowds, 🩺 Dr. Stethoscope hands the magnifier to 🌍 Guide Blue Planet: look down — the ground we build, farm, and run on is just a surprisingly thin shell on Earth's surface.

第 1 步：薄得像鸡蛋壳Step 1: Thin as an eggshell

地球这么大，地壳到底有多薄？The Earth is huge — so how thin is the crust, really?

地球剖面和鸡蛋对比：地壳像鸡蛋壳一样薄 — 地球半径约 6400 公里，地壳只有几到几十公里——比例和鸡蛋壳裹着鸡蛋一模一样。它是地球最外层的固体岩石圈，我们全部的生活都发生在这层“壳”上。 Earth's radius is about 6400 km, but the crust is only a few to tens of km — exactly the ratio of an eggshell around its egg. It is Earth's outermost solid rocky shell, and all of our lives happen on this "shell".

薄归薄，到处都一样薄吗？Thin, yes — but is it equally thin everywhere?

第 2 步：大陆厚，大洋薄Step 2: Thick continents, thin oceans

大陆地壳厚大洋地壳薄对比 — 不一样。托着高山大陆的地壳厚，约 30~70 公里；铺在海水下的大洋地壳薄，只有约 5~10 公里，又薄又年轻。记住口诀：大陆厚、大洋薄。 Not at all. The crust holding up mountainous continents is thick — about 30–70 km; the oceanic crust under the seas is thin, only about 5–10 km, thin and young. Remember: thick continents, thin oceans.

这层薄壳里，装的都是什么石头？What is this thin shell actually made of?

第 3 步：氧最多，硅第二Step 3: Oxygen first, silicon second

地壳元素占比条：氧硅铝铁 — 地壳里近一半是氧（约 46%），第二是硅（约 28%），再往后是铝（约 8%）和铁（约 5%）。你捡起的每块石头，基本都是氧和硅搭成的。 Nearly half the crust is oxygen (~46%), runner-up silicon (~28%), then aluminium (~8%) and iron (~5%). Almost every stone you pick up is built from oxygen plus silicon.

🌍 你来当钳工（30 秒）🌍 Your turn: work the bench (30 seconds)

道理讲完了。先拖放大滑块，看地壳从一条线变成一条带；再闯 4 关：厚度与元素。Theory done. First drag the zoom slider and watch the crust grow from a line into a band; then clear 4 levels on thickness and elements.

一句话记住它：地壳 = 地球最外层的固体薄壳，薄如鸡蛋壳；大陆厚、大洋薄；氧最多、硅第二。 Remember it in one line: the crust = Earth's outermost solid shell, thin as an eggshell; thick continents, thin oceans; oxygen first, silicon second.

极薄：半径 6400 公里，地壳只有几到几十公里Super thin: radius 6400 km, crust only a few to tens of km 大陆 30~70 公里，大洋 5~10 公里Continents 30–70 km, oceans 5–10 km 氧约 46%、硅约 28%、铝约 8%、铁约 5%Oxygen ~46%, silicon ~28%, aluminium ~8%, iron ~5%

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