I think that the answer is: Deep ocean water masses are classified based on flora's <span>calorific value.</span>
Basically the Earth is layered because of gravity. The earth formed in the molten state. The liquid iron which is very dense fell to the center. The rest of the earth is made up of silicate materials with SiO2 being the main component.
hope this helps!
30 °C is around the average temperature during summer
