Tornadoes form when warm, humid air collides with cold, dry air. The denser cold air is pushed over the warm air, usually producing thunderstorms. The warm air rises through the colder air, causing an updraft. The updraft will begin to rotate if winds vary sharply in speed or direction1
Population distribution and density patterns can be useful to understand because they help to explain how and why people migrate and develop in certain places around the world. These factors influence human migration and development and are therefore important to understand if you seek to understand how the world has developed over time and what are the forces that are driving this development.
