What led to the beginning of this eraij
I assume that you mean Age and not era. Nothing led to it. It's beginning is represented by an abrupt change in ratios of oxygen isotopes in layers of a stalagmite from the Meghalaya caves. This same isotopic signal has been found in ice cores in glaciers and lake bed sediments worldwide. This isotopic signal is interpreted to represent an abrupt change in climate worldwide. That climate changed caused changes in the intensity and frequency of monsoons leading to significantly less rainfall, which in turn seriously impacted cities that had developed in the Indus River Valley.
Classification of Earth is calculated in millions of years. How does this affect mankindij
Most geological units in the Geological Time Scale are, indeed, millions of years long. But the Holocene is unusual in that it is the shortest (11,700 years). However, the Holocene is important because it is so close to the present, and hence the evidence in the stratigraphic record is exceptionally well-preserved. It is also the period when humans developed agriculture, and when industrialisation spread across the globe leading to the development of our contemporary society.
But if we go further back into geological time, we can see how humans actually evolved and migrated, initially out of Africa, and gradually into Asia and Europe. All this occurred before the Holocene, although the peopling of the Americas is thought to have begun only a few thousand years before the onset of the Holocene.
What is a geological age and how is it calculatedij
Age is a term for an interval of geologic time that is based on a geologic rocks (rocks and strata). They vary in duration, one from the other, just as the durations of English monarchs vary in duration. We, of course, want to determine as accurately as possibly the number of years before the present that each unit began and when it ends (and the next unit begins). Many different dating techniques are used, and they provide calibrated ages of varying degrees of accuracy, which we are always trying to improve. Note the term calibrated age refers to the number of years before the present in contrast to Age (example Meghalayan Age) that is a formal time unit of lowest rank on the Geologic Time Scale.
What is Anthropoceneij The reason why some feel the need to include this time segment in the history of the Earthij
The Anthropocene has been championed by some as the younger interval in earth history when human activities have impacted the Earth system (for example the human induced climate change) and left a geologic record. For example, plastic in sea-floor sediments. Although this term has gained much publicity and is widely used, a formal proposed for this unit has never been prepared and submitted to the ICS for evaluation and consideration. Such a submission must establish a firm geologic foundation (rock/strata record) on which to define the unit. That has not been done.