When it comes to volcanoes, the term volcanic activity usually refers to what is going on in the volcano and there are various types of volcanic activity. At various stages in a volcanoes ‘life’ various things could and do happen because of its age, the kind of eruptions that have taken place in the past and/or are about to take place in the future. Usually, the less the types of volcanic activity, the better because that means that the chances of the volcano erupting again are reduced and so it would be unlikely that it would erupt any time soon.
Despite what was mentioned above, there is no particular way of determining the types of volcanic activity that a volcano may be going through until and unless research is carried out and that is precisely what geologists and scientists do to determine these- research. One of the types of volcanic activity includes unrest. Some volcanoes may show possibilities of erupting after unexpectedly major earthquakes. Since the tectonic plates move and bump into one another causing earthquakes, this could very well cause a volcanic eruption too thus affecting the types of volcanic activity there is.
Then there are those types of volcanic activity which show that the volcano itself has low to minimal chances of erupting ever again and that these are dormant. Dormant volcanoes are those which, in the past, erupted a lot and there eruptions were so extreme and major that any of the many types of volcanic activity are unlikely to happen again in the near future. This is because they do not have the ‘energy’ to erupt and become active again as most of its contents and lava erupted years ago leaving the ‘drained’ and this is why they are unlikely to experience any of the various types of volcanic activity in the near future. Note that these types of volcano are dormant, not extinct nor inactive- this means that they can erupt but the chances of eruption are less than the more active ones.
Of all the types of volcanic activity that volcanoes experience, active ones are the most dangerous because this means that they can erupt any time and if they have erupted recently that does not mean that they cannot or will not again. That just means that there are chances of them erupting at any point in the near future. How ‘near’ this ‘future’ is has yet to be determined.
In extinct volcanoes you can expect there to be none of the various types of volcanic activity simply because they are extinct which means that they do not have the lava or magma required for them to erupt and do not seem to have the energy to erupt ever again. These are different from dormant volcanoes because there are absolutely no chances that they will ever erupt or show any types of volcanic activity in the future. These types of volcanoes have usually been extinct for 10 millenniums and hence, are considered extinct.