The Oceans & Seas
Did you read the previous post? Did you realise what material I was referring to? Yes, it is water! In fact, water is SO important, I thought I would finish this set of readings by looking at water in depth. [There’s a joke there; do you get it? ‘In depth’? Water? Get it?]
So, let’s continue thinking about water.
All the water on the earth is in a closed system, which means that the total amount cannot increase or decrease – and this water exists in …
– the oceans and seas, as salt water,
– lakes, rivers, dams and reservoirs, as fresh water,
– ice sheets, mostly in Antarctica, as ice,
– clouds, or as water vapour in the sky.
The overwhelming bulk (97%) of the earth’s water lies in its oceans – hence the above picture. There are three major oceans: the Pacific, the Atlantic, and the Indian. The Pacific is by far the biggest and the deepest, and consequently holds over half of all the water on the earth.
We know about the surface of the ocean, where the friction of the wind over large areas causes constant motion in the form of waves which we can all see (again, the above picture), but it is interesting to note that we, human beings, still know very little about the deepest parts of the ocean. These parts are called the ‘abyssal plains’, and cover more than half of the planet’s surface, and are still very mysterious places. The reason for this is that it’s dark and extremely difficult to get down there.
The biggest problem being in the depths of the ocean is the pressure of the water. ‘Submersibles’ [the general name for craft that go down to the bottoms of the oceans] are hollow, and if there are people inside, need a supply of oxygen. They also need to be controlled carefully and need scientific instruments, which presents great technical challenges.
The deeper the submersible goes, the greater the weight of water which rests on top of it. If you go down to the deepest part – the Mariana Trench, near the island of Guam in the Pacific – the pressure of that water is enormous, about eight tons per square inch (which is over 1000 times greater than at the surface). This is similar to having 100 large elephants standing on your head, and just one reason why this spot has only been visited by people four times.
Can you explain the double meaning of ‘in depth’ in the first paragraph? ……………………..……………
Where, specifically, is most of earth’s water? …….……………..………
What is the greatest challenge about travelling to the bottom of the ocean? ……………………….……….…….
What is the name of the deepest part? ………………………………
Do you know the meaning of the underlined words?
To be mysterious
To be enormous
By the way, you can find out more about me at www.aisielts.com .