The difference between natural and human-made disasters is that human-made disasters occur as a result of human action, while natural disaster occur due to forces of nature. Natural disasters are disasters that take place regardless of human action, but human action can increase the likelihood and impact of natural disasters, and nature can influence the likelihood and impact of human-made disasters.
All disasters are put into two main categories: natural and human-made. According to RestoreYourEconomy.org, natural disasters include droughts, earthquakes, floods, tornadoes, wildfire, sinkholes, blizzards, hail, agricultural pests, diseases and hurricanes. Human-made disasters include power blackouts, hazardous material spills, explosions, chemical or biological attacks, nuclear blasts and radiological emergencies.
The main difference is what creates the disaster. Humans are the only beings that can create nuclear power, so a nuclear blast is a human-made disaster. On the other hand, human action cannot create a hurricane. This can only be due to the forces of nature. Because of this, some people refer to natural disasters as "acts of God."
Disasters are placed in one category or another, but the actions of man and nature can influence each other. For instance, human activity can reduce the available water in a region, leading to wildfire and droughts. The actions of nature can also create human made disasters, such as storms knocking out electrical equipment or causing chemical spills.