How come all the water on earth doesn't seep down into the earth and just disappear ?

Answer 1

Water is less dense than rock. So, the water effectively "floats" on top of the rock; just like oil floats on top of water.
If you are talking about the water seeping into cracks and the space between grains of sand, then my answer is that the water does fill these cracks and spaces and there is still plenty to go around.

Answer 2

The answer is truly as simple as density. When the building blocks of water are liberated from the earth (where it is stored in minerals as constituent parts of the mineral structure) it forms a compound (H2O) which is less dense than rock. Liquid water (like atmospheric gases) therefore tends to rise due to buoyancy. Water does seep into cracks and is sometimes forced into rocks by pressure gradients, but this circulation only proceeds until the pressure is exceeded by the buoyancy.

A simple experiment will demonstrate this. Get a cup of water and a turkey baster or syringe full of oil. Inject the oil into the bottom of the glass and walk away. Come back in awhile, and low and behold all the oil will have risen to the surface. This is a short term, simplified version of what's been going on in the planet for several billion years. The less dense material rises buoyantly, so the earth is actually "layered" from most dense material in the center (Fe-Ni core) and least dense at the outside (atmosphere).

Answer 3

Just like the two other people said up above, but also precipitation is always happening. It makes sure that no water on earth is lost nor gained. so the water stays here and the two up above had a very good point.

Answer 4

Because a certain distance down there is this stuff called bed rock which is impermiable to water. Although some rock will soak up water and allow it to slowly move, when you pile rock on rock, it gets smunched solid (metamorphosis) and no water passes through it. Also some clay soils, although not rock, will not pass water because they have such fine particles the water sticks them together and sticks to them so surface tension prevents further penetration. Clay is used in land fills to prevent messy water leakage.

Answer 5

When God was making water, he made plenty so there would always be enought to go around. He made plenty of oil too, he just did not expect us to be such energy hogs. Well maybe he did, maybe we have enought to last till we run out of time. Maybe that time is near, Nothing says that this world will continue for every.