Pre-Cambrian
The Pre -Cambrian period spans the time from birth of the earth, a staggering 4.6 billion years ago right up to the start of the Cambrian period, a time span estimated to be approximately 4 billion years. In the beginning the earth was just a ball of hot gas, as this gas cooled it started to solidify and form a hard crust. The cooling also caused water vapour to form and fall as rain, the rain then formed rivers and seas. The movement of the rivers and seas then caused the erosion of the crust that had formed. This was then carried as sediments and deposited to form layers at other areas of the earth. These layers became dried and hardened over time to form rocks. Volcanoes heated and changed some rocks while earth movements, quakes and pressure changed and distorted others. Movements and quakes caused many of the horizontal layers of sediments to be lifted moved and turned so much that instead of being horizontal, some were now at various degrees vertical, folded in places and Twisted in others. The pre - Cambrian period saw many changes to the earth, mountains formed and eroded away again, rivers and seas eroded the land and dropped their sediments forming more land, volcanoes spilled their larva and formed more land and earthquakes changed the moved landscape. These changes are still happening today all round our world but on a much much lesser degree. Early Pre-Cambrian was a very violent and hostile time of the young earth, so much so that the earth couldn’t support any form of life.
The late Pre-Cambrian saw the beginning of the earliest life forms about 3.5 billion years ago, these were of algae and bacteria and probably started in the warm seas, soft-bodied life followed later at around 700 to 600 million years ago. We very rarely find fossils from this time as not only were some of them very small but their soft bodies did not fossilise well. We occasionally find their imprints and burrows but they are rare finds indeed. The very first soft -bodied animal life was of jellyfish and worms. No life existed on land, only sea creatures developed at this time.
