GENERAL GEOLOGY

Detailed explanation-1: -In formal usage, eons are the longest portions of geologic time (eras are the second-longest). Three eons are recognized: the Phanerozoic Eon (dating from the present back to the beginning of the Cambrian Period), the Proterozoic Eon, and the Archean Eon. Less formally, eon often refers to a span of one billion years.

Detailed explanation-2: -eon = The largest unit of time. era = A unit of time shorter than an eon but longer than a period. period = A unit of time shorter than an era but longer than epoch. epoch = A unit of time shorter than a period but longer than an age.

Detailed explanation-3: -The word for the longest measurement of time is kalpa, Hindi for 432 billion years. A year is the time it takes for the earth to revolve around the sun once.

Detailed explanation-4: -The measurement of time began with the invention of sundials in ancient Egypt some time prior to 1500 B.C. However, the time the Egyptians measured was not the same as the time today’s clocks measure. For the Egyptians, and indeed for a further three millennia, the basic unit of time was the period of daylight.

Detailed explanation-5: -Some of the basic units of time are second, minute, hour, day, week, month, and year.