Oceans and seas

     Oceans cover almost three quarters of the earth. Near coast they are often quite shallow, but in some places they can be over 10km (6miles) deep-more than enough to submerge a mountain the height of Mount Everest. If you threw a coin into water this deep, it would take more than an hour to reach the bottom . The surface and the seabed teem with life, but in between is an emptier world.

 
  why is seawater salty?

=If you have ever swallowed seawater while
swimming , you'll know that it is too salty to drink.This salt comes from rocks in the Earth's crust that have been dissolved by rain seeping throughbthe ground. Most of the salt is the kind we use on our food. If all the seawater evaporated and the salt was left behind, it would form a layer 55m (180 ft)deep.


  if we could walk on the seabed, what would it be like?
=in many places you would disappear,because you would sink into a deep layer of soft and slimy ooze.this ooze forms from the skeletons of tiny plants and animals that drift down  to the seabed after they die. the ooze forms at an amazingly slow rate- just a few millimetres a century-but it has been building up for so long that in some places it is several metres deep.