You will have often heard or read about Holocene volcanoes or Pleistocene volcanoes, but what does this mean?
First you need to understand the word used for these periods of time. An Epoch is the beginning of a period of time according to the dictionary definitions:
Unfortunately geologists do it differently (well sort of). In geology an epoch is a period of time. Whereas the normal definition has the epoch as the start of an era (If you were born on 01 Jan 1970 that is your Epoch and from then until present is your Era) in geology the epoch is part of a ‘period’ which is part of an ‘era’.
The Holocene is an epoch and began about 11,700 years ago and includes from then right up to today, so if a volcano is described as Holocene it basically means that it has been active in the last 11,700 years.
The Holocene epoch is in the Quaternary period of the Cenozoic era, and just to confuse you even further this is in the Phanerozoic eon. Geologists!
The Pleistocene epoch, the one before the Holocene epoch, is – well yes an epoch in the Quaternary period. Actually it is the first one in that period. The Pleistocene is from around 2.5 million years ago until about 11,700 years ago. If you look on Wikipedia (click the image below) you will see this division of time:
Basically however as far as volcanoes are concerned all we need to know is are they Holocene or Pleistocene, in other words have they erupted in the last 11,700 years or not! Simple as that really.
Note that a volcano that erupted last week is a Holocene volcano – Nabro for example, just as much as one that has not erupted for thousands of years – Chaiten (Chile) before it erupted in 2008 as an example.
You will find a definition of Holocene in Wikipedia.
[RANT]You will also see a reference there to the Anthropocene. Despite what Wikipedia says:
Given these, a new synonym Anthropocene, is specifically proposed and used for the time period since approximately synchronous lithospheric evidence, or more recently atmospheric evidence, of human impacts have been found on the Earth and its ecosystems; these impacts may be considered of global significance for future evolution of living species.
this is nothing short of an obscene attempt by the AGW crowd to try and stamp their mark on history. Humans have had an impact on Earth since they have been around – maybe a million years or more – and this suggestion is just more ‘warmist’ BS.
The Holocene can be subdivided into five time intervals, or chronozones, based on climatic fluctuations:
* Preboreal (10 ka – 9 ka),
* Boreal (9 ka – 8 ka),
* Atlantic (8 ka – 5 ka),
* Subboreal (5 ka – 2.5 ka) and
* Subatlantic (2.5 ka – present).
At best it could be described as a chronozone.