Distinguish among eons, eras, periods, and epochs, using specific examples.

In a particular context, “epoch” can refer to a particular point of time characterized by a particular event/series of events.

While “era” refers to a period of time characterized by events in a chronological order.

Thus, an “era” can encompass more than one “epoch”.

“Period” can refer to a short interval of time or a very long interval of time.
For example:

“Eon” refers to an indefinitely long time. Eon is presumed to consist of at least 2 eras.

Eras, Eons, Epochs and Periods are the division and subdivisions of geological time scale based on the changes in the  geography, geology, climate and other characteristics of the earth.

The sequence of the various divisions depends on the length of each unit of time relative to each other.

sequence of time period is as follows:

Eons > Eras > Periods > Epochs

1.Eons-The longest division of time scale which lasts for billion of years.

            Geologists recognised three major Eons as:  

                                               Phanerozoic Eon (570-present)

                                               Proterozoic Eon (2500-570 mya)

                                                Archean Eon (3800-2500 mya)

2.Eras-eras are the subdivision of Eons which froms the second longest division of time scale. Eras can lasts for tens to hundreds miliion of years.

                  These are recognised as:

                           Coenozoic Era (66 mya-present)

                            Mesozoic Era (66-240 mya)

                             Paleozoic Era (240-570 mya)

.

3. Periods- Subdivion of time scale which is relatively shorter in time length.

periods can last for tens to  million of year

Geologists have divided eras into periods-

Coenozoic Era

                               Quaternary-(present)- Evolution of humans

                                Tertiary- Mammals diversified

Mesozoic Era

                               Cretaceous-extiction of dinosaurus

                               Jurassic-Dinosaurus diversified

                               Permian- age of mammals

Paleozoic Era

                              Pennysylvian-First reptiles

                              Mississipian-seed ferns

                              Devonian-first amphibians

                              Slurian-first land plants

                              Ordovician - metazoan diversification

                              Cambrian-first fishes

4.Epochs- subdivision longer than an age but shorter than a period .

                  Epoch can last for tens of million years.

why many students visually perceive stem as a vapid class?

for many students, however, stem subjects are optically discerned as vapid, tedious, and destitute of authentic-world applications. science and math have always been a major part of the high school curriculum, but many students have disengaged from these subjects because they don’t optically discern that they have any pertinence to the authentic world or students’ daily lives. for them, math and science have become a set of rules, procedures, laws, theorems, and formulas to memorize. some students even develop math apprehensiveness and cerebrate they are incapable of learning higher-level mathematics.

why is stem paramount?

as the u.s. economy changes, the ordinant dictation for stem-capable workers is growing. in may of 2014, the u.s. bureau of labor statistics counted more than 8.3 million stem jobs, which accounted for 6.2 percent of total employment in the cumulated states. that number is expected to perpetuate to increment as u.s. companies grow and innovate to compete in the ecumenical economy. according to the u.s. department of labor, the average salary for all stem jobs is $85,570, which is virtually double the average salary for all jobs.

many people still envision stem professionals as wearing a white lab coat and conducting research in a laboratory. in authenticity, some of the most in-demand stem fields are petroleum engineering, process engineering, and computer engineering. these fields that are experiencing shortages of qualified candidates are additionally among the highest paying, with the average petroleum engineer earning an annual salary of $147,520 in may 2014 according to the u.s. bureau of labor statistics.

in additament, stem subjects edify students valuable skills that are vital for prosperity in all vocations, even those that do not directly require stem erudition. engagement in stem subjects avails students develop quandary-solving, critical mentally conceiving, and leadership skills. these skills are so ecumenical, in fact, that statistics relinquished in the summer of 2013 by the u.s. census bureau designated that about three-quarters of the people with a bachelor’s degree in stem fields are not working in those vocations. many non-stem employers are poaching stem-qualified job candidates because they are more ingenious and collaborative than their non-stem counterparts.

as the ecumenical economy perpetuates to evolve, the desideratum for stem-capable workers will perpetuate to grow. by getting edifiers and students involved in the stem kineticism, an incipient generation of adroit workers will be poised to energize and expand this exhilarating field.

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