Historical Geology 
Vastness of time 
The act of comprehending is defined as a person's ability to understand a concept completely. When a human attempts to understand geological time they run into the problem of understanding numbers. Let's assume that understanding is related to experience. The number “10” is easy to understand since not only is it easy to count even as a child, but a standard human hand has ten digits. Let's continue that assumption and view “100”. The number takes long to count, but it can be done in minutes and can be viewed easily.
10 randomly select people were timed for their ability to count in a clear and understandable fashion. The average time to count ten seconds was 3.75 seconds. The average showed that every second a person is able to count 2 single digit numbers. We will assume I can keep this pace even as the number of symbols of the pronunciation of the number increases such as saying “9” compared to “9,999” and use a precision of whole numbers for seconds.
|Number||Time required to count|
|1,000,000||5 days 18 hours 53 min 20 sec|
|1,000,000,000||15 years 312 days 0 hours 53 min 20 sec|
The time required to count to one billion would take a person almost 16 years to count if they count at a continual pace. Earth is currently thought to be 4.5 billion years old. Just counting to that number would take about 70 years. That's nearly a human lifetime. This number is simply incomprehensible due to its vastness.
Geological Time 
Geology Time and a Clock 
Each geological time unit can represent a unit of daily time. An Eon can stand for hours, era for minutes, periods for second, and epoch for milliseconds.
As the animation shows. Time starts at the beginning of the Earth and continues to the present 4.6 billion years later. Eons change and has Eons move on Era's change. Era are a division of Eon's. This is the same for Periods and Epochs. The units of time increase in precision and decrease in scale. Comparing the Eon clock rotation to the Epoch rotation and u see how small Epoch and even Eras are in the scale of geological time.
The geological time scale is measured in Million Years Ago(Mya)