A more thorough explanation:

Ultrahazardous Activity is when someone does something that is very dangerous and likely to cause harm to people or property. This type of activity is also called abnormally dangerous or extrahazardous activity. When someone does an ultrahazardous activity, they are usually held responsible for any harm that results, even if they didn't mean to cause it. This is called strict liability.

For example, blasting rocks is an ultrahazardous activity because it can cause damage over a large area and the person doing the blasting may not have complete control over where the rocks go. If someone is hurt or their property is damaged because of the blasting, the person doing the blasting is usually responsible for paying for the damages.

Another example of an ultrahazardous activity is storing explosives near a residential area. Even though the chances of something bad happening may be small, the potential for harm is so great that it is considered an ultrahazardous activity.

Courts look at several factors to determine if an activity is ultrahazardous, including the likelihood and severity of potential harm, how common the activity is, and whether the activity is necessary for the public good. If an activity is found to be ultrahazardous, the person doing the activity is usually held responsible for any harm that results, even if they were careful and didn't mean to cause any harm.