The wonders of the past.  We all have a fascination with what has gone before, be it billions of years ago, or only a few hundred.  From the origins of our own families to the origins of the universe itself, we are compelled to look back and gather the evidence that we need in order to build a coherent picture.  It is sometimes difficult to actually believe that the world was once very different, that Dinosaurs roamed the lands, or that where you live may have once been at the bottom of an ocean.  The time frames often involved are even more difficult to imagine.  Sure, we can understand what a million years entails, but how well can we truly conceptualize it?

The purpose of this site is to explore our past, bit by bit, and to hopefully increase understanding.  I've divided up the journey into the well known geological periods, and from there we'll look at various aspects of the time.  The initial periods, found on this page, are of my own devising, separating the pre-Solar System eons according to what seems like, at the moment, logical sections.  Revisions are, of course, always underway (not to mention site construction).

Uage unknownBig Bang Eon 13.5 billion to 12.5 billion years ago:  Not a proper eon perhaps, but this is what I hope to be a logical division spanning the time from the creation of the universe, to the formation of the earliest galaxies.  Remarkably, the greatest amount of change during this eon was in the first few seconds, when the entire nature of the Universe was determined.  Some believe that it was random, others believe that it was preordained.  Whatever the case, everything that we can see, know, or hope to understand was born in a rush of energy originating from a singularity point no larger than a pin head.  Our universe, some 13 billion light years and more in size, began as a spot smaller than the period at the end of this sentence, a spot that was unimaginably hot and dense.

 

Hubble-NASA image, Public DomainGalactic Formation Eon 12.5 billion to 10 billion years ago:  Another eon that I have given name to in the interests of clarity, this period encompasses the period of time from the formation of the earliest galaxies, to the birth of the first stars with significant amounts of heavy elements in them, something that allowed for the formation of the first terrestrial planets.  These first galaxies have actually been imaged by the Hubble Space Telescope, faint nebulosities found behind the sharper, clearer images of nearby galaxies.  Hold a dime up at arm's length, and imagine it crammed full of several hundred million galaxies.  That is the amount of ancient galaxies that can be spied with the proper instrument... add that to cover the entire sky, and you begin to get an image of just how vast the Universe is.

 

Hubble-NASA, Public Domain imageStellar Heavy Element Eon 10 billion to 4.66 billion years ago:  Yet another chronological division on my part.  Here is where we start to shift to a Solar System-centric point of view, for I've made this eon last from the roughly defined period of time when stars rich in heavy elements began to form, to the beginning of the formation of our own Solar System.  In the early part of this eon, metal-rich stars were still fairly rare, and their metal content was less than what one finds in "modern" stars.  However, with each death of a star, more and more heavy metals are spewed out into the galaxy, and used to form stars even more metal rich.  It is in this eon that the odds for the formation of a life-bearing planet become greater and greater, until finally it is a certainty in at least one case -- our own Earth.

 

copyright William K. Hartmann; Used with permission; www.psi.edu/hartmannSolar System Formation Eon 4.66 billion to 4.56 billion years ago:  This is the last of the self-named eons on my part, and is meant to cover the time span during the formation of our Solar System, from its earliest beginnings, to the point just before the oldest known geological record can be determined.  This was a period of hot and fast planetary formation, with the formation of worlds from dust, and their runaway growth into the planets we know today.  Much is still uncertain about just how the planets formed, but as our research continues, the answers are slowly becoming more evident.  Even so, it is difficult to imagine that a rocky, meteor-plagued world covered in oceans of magma, would one day become the comparatively quiet blue and white marble of Earth.

 


 (image copyright Don Dixon; used with permission)

Hadean Eon 4.56 billion to 3.85 billion years ago:  The name of this era is fairly self-explanatory;  Earth was in the final throws of her formation, with the outgassing of the atmosphere through planet-wide volcanism, the oceans falling as torrential rainstorms that lasted tens of thousands of years, and the ongoing massive bombardment by left over planetary debris.  It was a world that was hostile to life.  And yet, it appears that as soon as conditions were viable for it, life did indeed appear.  Whether it was crowded about deep sea thermal vents, or in the form of the archetypical "pond scum", the earliest forms of life were tenacious in the face of the harsh planet, and would eventually give rise to everything from mice to dinosaurs to men.  Last updated  November 21, 2003

 


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 Archean Eon 3.85 billion to 2.47 billion years ago:  The Archean saw the rise and spread of anaerobic bacteria across the surface of the Earth, which remain swaddled in a haze of brown methane.  But towards the end of the eon, aerobic forms of life had appeared, poisoning that pristine atmosphere with oxygen, leading to massive die-offs, and the bluing of the sky.  The tectonic engine that would shape the continents began to run in earnest, and the meteoric bombardment came to an end.  The Earth had begun to settle into a much calmer routine.  It was still a long ways to anything that we would recognize, but by the end of the Archean the planet had become what we would term "habitable".  Last updated  December 15, 2003

 


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 Proterozoic Eon 2.47 billion to 570 million years ago:  With the oxygenating of the Earth, life began to spread even further, and to develop into new and more complex forms.  By the end of the Eon, the first metazoan forms had appeared, multicellular animals of substantial size, the forbearers of all following forms of life.  The Earth itself continued to settle into something more familiar as the protocontinents formed and reformed into supercontinents.  Ice ages advanced and retreated, and at least one period of runaway glaciation produced a "snowball Earth", where most of the planet had become covered in ice kilometers thick.  Last updated  December 15, 2003

 

Usage unknownPhanerozoic Eon 570 million years ago to the Present:  This is the eon in which we live, and which has seen the rise and fall of nearly all the metazoan groups.  Woolly mammoth, dinosaurs, the first amphibians to crawl from the sea, all of this has come to pass in the current eon, and doubtless it will continue onward until finally, anywhere from 500 million to 2 billion years from now, life will face its final and complete extinction as the Sun expands on the way to its own preordained funeral.  Last updated  December 15, 2003

 

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Contents © John M. and Margo L. Dollan 2003
Other usage cited at Usage Permission Page
This Page first uploaded October 7, 2003
Most recent update for this page December 15, 2003