The available disasters are:
When starting a disaster, you have varying degrees of control over the disaster, from being able to pick the start location, to actually controlling the behavior of the disaster.
Fires can be started through the Disaster Menu, but are also likely to happen spontaneously. The likelihood of a fire occurring is directly related to flammability - high flammability locations are more likely to have fires. Thus, you can reduce your chance of having fires by taking steps to reduce flammability in your city. Fires can also occur as secondary disasters, following an earthquake, meteor, or riot, for example. You can respond to fires by dispatching fire trucks and planes to the location of the fire using the Emergency Tools in the Mayor Mode toolbar.
Unlike other disasters, riots cannot be directly started through the Disasters Menu, they can only happen spontaneously. However, you can increase the chances of having riots in your city by reducing police coverage and reducing funding to city services, such as education and healthcare. Riots will often follow upon a strike. You can respond to riots by dispatching police cars and helicopters to the location of the riot using the Emergency tools in the Mayor Mode toolbar.