在我们星球海洋的波浪深处有一些地方，就像我们大气层的上游一样，它们在我们的表面上离我们很远。这些地区是深海战壕。这些是海底长而窄的凹陷，延伸得如此之深，以至于它们的生命形态和条件曾被认为是“未知的”。这些黑暗，曾经神秘的峡谷深入地下11,000米（36,000英尺）深入我们的地壳。这太深了，如果珠穆朗玛峰被放置在最深的海沟的底部，它的岩石峰值将在太平洋波浪下方1.6公里处。战壕是一些非常惊人的地形。海底本身包含的火山和山脉高于任何大陆山峰。深海海沟比任何大陆峡谷都要矮。这些战壕是如何形成的？简短的答案来自地球科学和构造板块运动的研究，这些运动适用于地震以及火山活动。地球科学家知道，深层岩石在地球的熔融地幔层上运行。当它们漂浮在一起时，这些“板块”相互挤压。在地球上的许多地方，一个盘子在另一个盘子下潜。它们相遇的边界是深海沟的存在。例如，位于马里亚纳岛附近且距离日本海岸不远的太平洋下的马里亚纳海沟是所谓“俯冲”的产物。在沟槽下方，欧亚板块正在一个较小的板块上滑动，称为菲律宾板块，它沉入地幔并融化。沉没和融化形成了马里亚纳海沟。海洋战壕遍布世界各地，构成了任何海洋中最深的部分。它们包括菲律宾海沟，汤加海沟，南三明治海沟，欧亚盆地和马洛伊深海，迪亚曼蒂纳海沟，波多黎各海沟和马里亚纳。大多数（但不是全部）与俯冲行动或板块分开直接相关，这需要数百万年才能发生。例如，当南极洲和澳大利亚在数百万年前分崩离析时形成的迪亚曼蒂纳海沟。这一行动破坏了地球的表面，由此产生的断裂带变成了海沟。大多数最深的战壕都是在太平洋上发现的，它们覆盖了所谓的“火环”。由于构造活动，该地区得名，这也促使深水下火山爆发的形成。 Mariana Trench的最低部分被称为Challenger Deep，它构成了战壕的最南端。它已被潜水艇以及使用声纳的水面舰艇（一种从海底反弹声音脉冲并测量信号返回所需时间的长度）进行了映射。并非所有战壕都像玛丽安娜一样深。时间似乎抹去了它们的存在。这是因为，随着年龄的增长，战壕中充满了海底沉积物（沙子，岩石，泥土和从海洋中较高处漂浮下来的死亡生物）。海底较旧的部分有较深的沟渠，这是因为较重的岩石会随着时间的推移而下沉。直到20世纪，这些深海战壕存在的事实仍然是一个秘密。那是因为没有船只可以探索这些地区。参观他们需要专门的潜水艇。这些深海峡谷对人类生活极其不利。虽然人们确实在上个世纪中叶之前将潜水钟发送到海洋中，但没有一个像壕沟一样深。在这些深处的水压会立即杀死一个人，因此在设计和测试安全船只之前，没有人敢冒险进入马里亚纳海沟的深处。这种情况在1960年发生了变化，当时有两名男子在一个叫做里雅斯特的深海潜水器中。 2012年（52年后）电影制片人和水下探险家詹姆斯卡梅隆（泰坦尼克号电影成名）在他的Deepsea Challenger工艺中冒险进入马里亚纳海沟底部的第一次单人旅行。大多数其他深海探险船，如阿尔文（由马萨诸塞州伍兹霍尔海洋研究所运营），目前几乎没有潜水，但仍然可以下降约3600米（约12,000英尺）。令人惊讶的是，尽管在沟渠底部存在高水压和低温，但在这些极端环境中生活仍然蓬勃发展。微小的单细胞生物生活在战壕中，以及某些类型的鱼类，甲壳类动物，水母，管虫和海参。此外，许多沟渠的底部都充满了火山口，称为“黑烟囱”。这些不断将熔岩和化学物质排放到深海中。然而，这些通风口远非不适宜，而是为所谓的“极端微生物”提供急需的营养素，这些生命可以在外星人的条件下生存。
There are places deep beneath the waves of our planet’s oceans that are as far away from us on the surface as the upper reaches of our atmosphere. These regions are the deep ocean trenches. These are long, narrow depressions on the seafloor, extending so deep that their life forms and conditions were once considered “unknown”. These dark, once-mysterious canyons plunge down as far as 11,000 meters (36,000 feet) into our planet’s crust. That’s so deep that if Mount Everest were placed at the bottom of the deepest trench, its rocky peak would be 1.6 kilometers beneath the waves of the Pacific Ocean. Trenches are some pretty amazing topography. The seafloor itself contains volcanoes and mountains that tower higher than any of the continental peaks. And the deep ocean trenches dwarf any of the continental canyons. How do those trenches form? The short answer comes from Earth science and the study of tectonic plate motions, which applies to earthquakes as well as to volcanic activity. Earth scientists know that deep layers of rock ride atop Earth’s molten mantle layer. As they float along, these “plates” jostle each other. In many places around the planet, one plate dives under another. The boundary where they meet is where deep ocean trenches exist. For example, the Mariana Trench, which lies beneath the Pacific Ocean near the Mariana island chain and not far from the coast of Japan, is the product of what’s called “subduction.” Beneath the trench, the Eurasian plate is sliding over a smaller one called the Philippine Plate, which is sinking into the mantle and melting. That sinking and melting formed the Mariana Trench. Ocean trenches are found around the world and make up the deepest part of any ocean. They include the Philippine Trench, Tonga Trench, the South Sandwich Trench, the Eurasian Basin and Malloy Deep, the Diamantina Trench, the Puerto Rican Trench, and the Mariana. Most (but not all) are directly related to subduction actions or plates moving apart, which take millions of years to occur. For example, the Diamantina Trench formed when Antarctica and Australia pulled apart many millions of years ago. That action cracked Earth’s surface and the resulting fracture zone became the trench. Most of the deepest trenches are found in the Pacific Ocean, which overlies the so-called “Ring of Fire”. That region gets the name due to tectonic activity that also spurs the formation of volcanic eruptions deep beneath the water. The lowest part of the Mariana Trench is called the Challenger Deep and it makes up the southernmost part of the trench. It has been mapped by submersible craft as well as surface ships using sonar (a method that bounces sound pulses from the sea bottom and measures the length of time it takes for the signal to return). Not all trenches are as deep as the Mariana. Time seems to erase their existence. That’s because, as they age, trenches are filled with sea-bottom sediments (sand, rock, mud, and dead creatures that float down from higher in the ocean). Older sections of the sea floor have deeper trenches, which happens because heavier rock tends to sink over time. The fact that these deep-ocean trenches existed at all remained a secret until well into the 20th century. That’s because there were no vessels that could explore those regions. Visiting them requires specialized submersible craft. These deep ocean canyons are extremely inhospitable to human life. Although people did send diving bells into the ocean prior to middle of the last century, none went as deep as a trench. The pressure of the water at those depths would instantly kill a person, so no one dared venture into the deeps of the Mariana Trench until a safe vessel was designed and tested. That changed in 1960 when two men descended in a bathyscaphe called the Trieste. In 2012 (52 years later) filmmaker and underwater explorer James Cameron (of Titanic film fame) ventured down in his Deepsea Challenger craft on the first solo trip to the bottom of the Mariana Trench. Most other deep-sea explorer vessels, such as Alvin (operated by the Woods Hole Oceanographic Institution in Massachusetts), do not dive nearly quite so far, but still can go down around 3,600 meters (around 12,000 feet). Surprisingly, despite the high water pressure and cold temperatures that exist at the bottoms of trenches, life does flourish in those extreme environments. Tiny one-celled organisms live in the trenches, as well as certain types of fish, crustaceans, jellyfish, tube worms, and sea cucumbers. In addition, the bottoms of many trenches are filled with volcanic vents, called “black smokers”. These continually vent lava and chemicals into the deep sea. Far from being inhospitable, however, these vents supply much-needed nutrients for types of life called “extremophiles”, which can survive in the alien conditions.