Plastic bottle sealed at 14000 feet (4,267 metres)
Picture 1: 14,000 feet (4,267 metres)
Picture 2: 9,000 feet (2,743 metres)
Picture 3: 1,000 feet (305 metres)
The air sealed in the bottle up a mountain at 4,267 metres was at a lower air pressure than the air lower down.
This graph shows how air pressure decreases with altitude (height)
Pressure is the force applied perpendicular (think about a right angle) to the surface of an object per unit area.
Pressure = a force pushing on an area.
Think about our bottle of air sealed at 4,267 metres up a mountain.
Lower down the air pressure outside of the bottle is much more than the air pressure inside the bottle so the bottle is crushed.
15 year sea level average air pressure; June, July & August = top map; December, January & February = bottom map.
Global Pressure Belts
This creates a band of rain and low air pressure on or around the Equator which moves North and south as the seasons change.
The band of clouds can be seen on satellite images.
The band of clouds is caused by air rising which causes low air pressure.
The clouds form rain and this where we get rainforests forming.
Eventually the air will cool and form a convection cell.
In a convection cell warm air rises.
After rising it cools and starts to sink.
The rising and sinking air forms roughly circular currents.
The most heat is received along the Equator; the air rises and splits into two convection cells. One to the North and one to the south.
Where the air sinks it creates a band of high pressure.
As air sinks it warms and any clouds/water vapour is evaporated so the skies are clear.
This is where and why we get hot deserts like the Sahara Desert at these latitudes.