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
Ingalba, Big Bush and Pucawan Nature Reserves Ordovician geology of quartzite, shale, slate, phyllite and schist. There is an indistinct boundary with the Upper Silurian geology predominant in Big Bush and Ingalba Nature Reserves. These areas consist of sandstone, shale, siltstone, slate, conglomerate and limestone, with some volcanics. Abundant but poorly preserved fossil graptolites are found in a disused quarry in Pucawan Nature Reserve. These fossils (an extinct group of oceanic colonial organisms) have been dated from the late Ordovician period. The soils are of intermediate loamy texture. Crest soils are mostly shallow, with broken shales and siltstone present on the surface. On the gentle slopes and