Volcano of classifying magmatic volcanoes is by their frequency of eruption, with those that erupt regularly called active, those that have erupted in historical times but are now quiet called dormant or inactive, and those that have not erupted in historical times called extinct. However, these popular classifications—extinct in particular—are practically meaningless to scientists. They use classifications which refer to a particular volcano's formative and eruptive processes and resulting shapes. There is no consensus among volcanologists on how to define an "active" volcano. The lifespan of a volcano can vary from months to several million years, making such a distinction sometimes
Active safety as they become more sophisticated, questions will need to be addressed regarding driver autonomy and at what point these systems should intervene if they believe a crash is likely. In engineering, active safety systems are systems activated in response to a safety problem or abnormal event. Such systems may be activated by a human operator, automatically by a computer driven system, or even mechanically. In nuclear engineering, active safety contrasts to passive safety in that it relies on operator or computer automated intervention, whereas passive safety systems rely on the laws of nature to make the reactor respond to dangerous