Simple Answer:
Warm air rises during convection. Perhaps better said, natural convection of air is the rising of less-dense warm air relative to the more-dense cold air.
This is a simple matter of buoyancy. Gravity pulls everything downward, but the pull is proportional to mass and items immersed in a fluid that have lower mass per unit volume than the fluid will tend to float, i.e. experience a buoyant force up as gravity pulls harder downward on the surrounding fluid.
Causes and Explanation:
Everyone says "Warm air rises" and that is an example of natural convection. Convection requires a fluid, heat source and gravity. The heat source causes a temperature gradient in the fluid so that buoyancy of the warmer fluid causes it to rise.
Buoyancy is the reasons bubbles rise and hot air balloons float and anything light, like a piece of wood, raises to the surface. The gravitational force experienced by a volume of material is just its weight, i.e. mass times gravity. Mass is the density of the material times its volume. So, if the object (like wood) has a lower density than water, the force of gravity on the object is less than the equivalent volume of water. The buoyant (upward) force is the difference in the wight of the object and the weight of the same volume of liquid.
Light objects experience the upward buoyant force and if the fluid (air or water or any fluid) is heated and expands, then it has a larger volume and less density and it also experiences the upward force.
The natural buoyancy of warmer fluids causes the force that moves the fluid and that movement is what we call natural convection.
Other Aspects:
cool air descends and hot air rises...joe..
heat
Convection currents in the magma drive plate tectonics.Heat generated from the radioactive decay of elements deep in the interior of the Earth creates magma (molten rock) in the aesthenosphere.
Because there are deep-ocean trenches which are deep under water canyons.
It is never stated what actually causes the zombies to rise up. That is part of what makes the series so frightening - the thought that something like this could just start happening for no reason.
they come in indirect contact
It is called Lift. The difference in pressure above and below the wigs as a bird moves through the air produces an upward force that causes the bird to rise.
Convection is the process that causes warm air to rise and cold air to sink. As such, the winds caused by this process are called convection currents.
Convection current
convection
convection
A convection current is how either water or air cools and heats. The thing that causes them is the heating and cooling of air or water which makes it rise or sink.
Convection current
The rock in a rising convection current is hotter and more buoyant than the surrounding rock, causing it to rise.
Convection causes it to rise, causing a valley breeze
Convection
Fluids rise and sink in a convection current due to differences in temperature and density. When a fluid is heated, it becomes less dense and rises, creating an upward flow. As it cools, it becomes more dense and sinks, creating a downward flow. This continuous cycle of heating and cooling drives the convection current.
Density.
Gravity causes the less dense stuff to rise