The oceans cover about 361 million square kilometers and they are all connected. The average depth of the ocean is 3750 meters. Over 90 percent of the Earth's species (types) of living things live in the oceans.
2.The deepest point in all the world's oceans is called Challenger Deep.
It is the Mariana Trench in the Pacific Ocean and is 10,923 meters deep - almost 11 kilometers. A tower of 3500 elephants, one on top of the next, could stand in it without touching the surface. In 1960, two explorers, Jacques Piccard and Don Walsh, visited the bottom of Challenger Deep in a diving vessel called Trieste.
V The Trieste, which made the deepest deep-sea dive ever in 1960, was made of a large tank full of gasoline to give buoyancy, with a small round passenger chamber fixed underneath. V
3.If you were sitting at the bottom of the deep ocean, you'd be squashed flat.
At great depths, the weight of all the water above presses from all sides. At the bottom of Challenger Deep, the water pressure is more than 1000 times stronger than at the surface. It's cold, too - only just above freezing point. People can only go there inside specially built diving machines with thick walls that can resist the pressure and cold.
V This map shows the ridges, trenches, plains, and mountains within the world's oceans, as well as those on land. V
4.One of the world's most extreme environments is found under the sea.
At hydrothermal vents, incredibly hot water bubbles out from inside the earth at temperatures of up to 400°C. Around the hot vents live unusual creatures such as giant tubeworms and sea spiders and tiny bacteria that feed on the minerals dissolved in the hot water. Hydrothermal vents were only discovered in 1977.
V A cross-section of the seabed. It usually slopes gently away from the shore, then drops steeply down to a flat plain. V
5.Sea level - the height of the sea - is about the same all over the world.
It changes over time, as the Earth's temperature varies. About 20,000 years ago, during the Ice Age, the sea level was 130 meters lower than it is now. At the moment, the sea level is rising because global warming is making ice melt at the poles.
大约70％的地球表面被海洋覆盖。
海洋覆盖约3.61亿平方公里，全部相连。海平面深度为3750米。超过90％的地球物种（类型）的生物都生活在海洋中。
2.世界上所有海洋的最深处都被称为“挑战者之深”。
这是太平洋的Mariana海沟，深10,923米，近11公里。 3500个大象的塔，一个在下一个的顶部，可以站在它，而不会碰到表面。 1960年，两名探险家雅克·皮卡（Jacques Piccard）和唐·沃尔什（Don Walsh）参观了一个名叫里雅斯特的潜水船的“挑战者深”（Challenger Deep）的底部。
五，1960年深入深海的深夜潜水的里雅斯特是由一个装满汽油的大型坦克组成的，这里有一个固定在下面的小型乘客舱。 V
如果你坐在深海的底部，你会被压扁。
在很大的深度，所有水面以上的压力机的重量。 “挑战者之深”底部的水压比表面强1000倍以上。它也很冷，只是在冰点之上。人们只能在那里专门制造的具有厚壁的潜水机，可以抵抗压力和感冒。
V这张地图显示了世界海洋以及陆地上的山脊，海沟，平原和山脉。 V
世界上最极端的环境之一是在海下发现的。
在热液喷口处，在高达400°C的温度下，从地球内部出现令人难以置信的热水气泡。在热风口周围，生活着不寻常的生物，如巨型管蠕虫和海蜘蛛，以及细小的细菌，可溶解于热水中的矿物质。水热通风口仅在1977年才发现。
V海底横截面。它通常从岸边轻轻地斜坡，然后急剧下降到平坦的平原。 V
海平面 - 海拔高度与世界各地相同。
随着时间的推移，随着地球温度的变化，大约2万年前，在冰河时代，海平面比现在低130米。目前，海平面上升，因为全球变暖正在使两极融冰。