Volcano an extinct volcano from a dormant (inactive) one. Dormant volcanoes are those that have not erupted for thousands of years, but are likely to erupt again in the future. Volcanoes are often considered to be extinct if there are no written records of its activity. Nevertheless, volcanoes may remain dormant for a long period of time. For example, Yellowstone has a repose/recharge period of around 700,000 years, and Toba of around 380,000 years. Vesuvius was described by Roman writers as having been covered with gardens and vineyards before its eruption of 79 CE, which destroyed the towns of Herculaneum and
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