Human stampedes are caused by overcrowding and crowd panic when a bunch of people try to move in one direction or other directions all at once.
Deadly human stampedes are not always caused by crowd panic, though — they can also be caused by entrapment in a limited area and physical strain.
As well as at religious pilgrimages, stampedes have caused deaths at sporting matches, music events and during emergency situations, such as fires and explosions.
A crush stampede is when a crowd of people moves in the same direction at the same time, some may collide and pile up against or on top of each other.
This can get very dangerous very quickly.
Experts refer to such an incident as a stampede, crowd surge, or crowd crush.
If you get caught in a stampede you should do the following.
Stay on your feet.
Conserve energy – don't push against the crowd and don't yell or scream.
Use sign language to communicate with those around you (point, wave, even use your eyes)
Keep your hands up by your chest, like a boxer – it allows you movement and protects your chest.
While you might think most injuries and deaths in such incidents are cause by trampling, a lack of oxygen is often to blame.
The crush of the crowd pushes against your chest and makes it hard to breathe, leading to what's called compressive asphyxia.
It can also cause head and neck injuries.
Crushes often occur during religious pilgrimages and large entertainment events, as they tend to involve dense crowds, with people closely surrounded on all sides.
Human stampedes and crushes also occur as people try to get away from a perceived danger, as in a case where a noxious gas was released in crowded premises.
On 24 September 2015, an event described as a "crush and stampede" caused deaths estimated at well over 2,000 people, suffocated or crushed during the annual Hajj pilgrimage in Mina, Mecca, Saudi Arabia, making it the deadliest Hajj disaster in history.