What causes convection to happen?
1 Answer
Unequal heating of the Earth.
Explanation:
The surface of the Earth does not heat evenly because different surfaces absorb or reflect more heat than others. For example, a black asphalt parking lot will absorb, for all intents and purposes, all the solar energy that reaches it. A grassy field on the other hand will reflect 10-25% of the solar energy that reaches it. As such the surface will heat unequally.
According to Charles's Law (one of the gas laws) as the temperature of a gas increases, the volume of the gas will also increase. Since the formula for density is mass over volume, an increase to temperature will lead to a decrease in density. So as the air over a black asphalt parking lot heats, it will expand and the density of that air will drop. The formula for buoyancy is a little complicated but the end result is as the density of the heat air drops in relation to the air surrounding it, it's buoyancy increases and it begins to rise. This rising of heated air parcels is convection.
If you need to know more about how the buoyancy formula works in relation to convection please let me know.
