🗺️ 海底地形：海平面下的“山川”🗺️ Seafloor Topography: Mountains Under the Sea
上一片里，蓝蓝在海面上追浪。这一片它穿上潜水服：海平面下面，有山川吗？有，而且比陆地更壮观。Last leaf, Lanlan chased waves on the surface. Now it pulls on a diving suit: are there mountains down there? Yes — grander than on land.
第 1 步：从岸边往外，四站越走越深Step 1: Four stops out from the shore, deeper each time
先跟蓝蓝开船，看海底剖面的四站。First, sail with Lanlan across the four seafloor stops.
第 1 站大陆架：200 米以浅，又浅又有营养，是渔场和石油的家。第 2 站大陆坡：陡坡直下深海。第 3 站深海平原：最宽最平的大地。第 4 站海沟：最深的裂缝。Stop 1, the shelf: shallower than 200 m, rich and sunny — home to fisheries and oil. Stop 2, the slope: a steep slide into the deep. Stop 3, the abyssal plain: the widest, flattest land. Stop 4, the trench: the deepest crack.
最深的海沟到底有多深？能装下珠峰吗？Just how deep is the deepest trench — could it swallow Everest?
第 2 步：马里亚纳海沟，倒放珠峰还装不满Step 2: Mariana — a flipped Everest still fits inside
马里亚纳海沟深约 11 千米，珠峰高 8849 米。把珠峰倒着放进海沟，顶上还差 2 千米才到海面。海底还在长大：大洋中脊涌出岩浆，把海底向两边推开。The Mariana Trench runs about 11 km deep; Everest stands 8,849 m tall. Flip Everest upside down into the trench and 2 km of water still sits above its peak. And the seafloor keeps growing: mid-ocean ridges spill lava that pushes the floor apart.
海底这么深，人类下不去，怎么画出这张地图？Too deep for divers — so how did we map it?
第 3 步：声呐喊一嗓子，听回声量水深Step 3: Shout with sonar, read the echo
测量叫“测深”，工具是声呐。船向海底发射声波，再听回声回来。回声越慢，水越深。船一边走一边喊，海底地图就画出来了。Measuring depth is called “sounding”, and the tool is sonar. The ship fires sound beams at the bottom and listens for echoes. Slower echo, deeper sea. Sail and shout all the way — and the map draws itself.
🎮 你来开测量船（30 秒）🎮 Your turn: drive the survey ship (30 seconds)
道理讲完了。先拖深度计走一趟，看深度和地形的变化；再闯下面 4 关，定位四个地形部位。Theory done. First drag the sounder across and watch depth and terrain change; then clear 4 rounds — locate all four zones.
一句话记住它：海底从浅到深是陆架、陆坡、平原、海沟；马里亚纳最深约 11 千米；声呐听回声测水深。Remember it in one line: shallow to deep goes shelf, slope, plain, trench; Mariana is deepest at ~11 km; sonar reads depth from echoes.
大陆架浅（200 米内）、陆坡陡、平原平、海沟深Shelf shallow (within 200 m), slope steep, plain flat, trench deep马里亚纳海沟约 11 千米，倒放珠峰还装不满Mariana runs ~11 km — a flipped Everest still fits inside声呐测深：发声波、听回声，回得越慢越深Sonar sounding: fire pings, hear echoes — slower means deeper
内容参考 OpenStax 等公开教材，多来源核对 · AI 生成、人工审核 · 发现错误欢迎指正，帮这片叶子长得更好。Based on OpenStax and other open textbooks, cross-checked across sources · AI-generated, human-reviewed · Spotted a mistake? Tell us — help this leaf grow.
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