A natural risk can be defined as the probability that a territory and the society that lives in it will be affected by natural episodes of extraordinary magnitude.[1]​ In other words, the vulnerability of a population or region to a natural threat or danger.

On the contrary, anthropic risks are risks caused by human action on nature, such as contamination of water, air or soil, deforestation or fires, among others.

The threat or natural danger refers to the probability that a certain natural phenomenon will occur, of a certain extent, intensity and duration, with the potential to cause damage to people or the environment.[1]​.

vulnerability refers to the impact of the phenomenon on society,[1]​ and it is precisely the increase in vulnerability that has led to a greater increase in natural risks. Vulnerability ranges from the use of the territory (risk exposure) to the structure of buildings and alarm and warning mechanisms (socioeconomic sensitivity), and depends strongly on the population's response capacity to risk (resilience).

The number of human disasters has increased in recent years because as the population grows, the number of people they affect is increasing. On the other hand, the transfer of many inhabitants to cities with the process of rural exodus accentuated especially in underdeveloped countries, means that when any incident occurs in the proximity of a large city the consequences are dramatic. A single earthquake, centered in the Chinese city of Tangshan, killed more than 250,000 people in 1977.

It is necessary to distinguish between:

• - Current risks: an erupting volcano, an active landslide, a contaminated aquifer that is being exploited. Current Risks are usually accompanied by damage, even if they have not developed their full potential.

• - Potential risks: for example, a temporarily inactive volcano or a slope in precarious balance. These concepts are often widely used in Risk Maps.

Natural risks can be classified as follows:

• - Geological:

• Volcanism

• Earthquakes