A hypothetical solid figure whose surface corresponds to mean sea level and it's imagined extension under(or over) land areas.
OCEANOGRAPHY is the study of world's oceans..
Importance of oceanography:it studies the plants and animals in the ocean that could have an effect on the weather...
1)it's largely unexplored
2)humans may have to habitate the oceans one day
3)it's a large source of food(plants and animals alike)
4)the medical possibilities that are waiting to be discovered
5)how the oceans effect global affect,coastal erosions,.......
Water gets more dense at 4 degrees that point,because water molecules are not spherical,they begin to exhibit tendency to hold particular orientations at preferred separation distances that keep them further apart that was possible about 4 C.cooling from 4 C to 0 C removes more kinetic energy allowing the preferred orientations and separations more orderly,further decreasing freezing,0C,the non spherical forces between molecules lock them into preferential orientations and seperations of the ice crystal arrangement with a sharp increase in avg. seperations and decrease in bulk density...
hence,density of water is maximum at 4 C....
As water molecules approach the freezing point, they need to expand to form ice crystals (as it changes form from a liquid to a 'solid'). Layman's terms!

Geoid ---- a hypothetical solid figure whose surface corresponds to mean sea level and its imagined extension under (or over) land areas.....

hope it will help :)

1 5 1