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
Dormant Commerce Clause Board of California", . In this case the Dormant Commerce Clause is no longer "dormant" and the issue is a Commerce Clause issue, requiring a determination of whether Congress has approved, preempted, or left untouched the state law at issue. The second exception is "market participation exception". This occurs when the state is acting "in the market", like a business or customer, rather than as a "market regulator". For example, when a state is contracting for the construction of a building or selling maps to state parks, rather than passing laws governing construction or dictating the price of state park