Planet Earth - The Mesoproterozoic Era - Calymmian Period

So with a few days until Christmas 2011, we enter Mesoproterozoic Era (1600 to 1000 million years ago) or the middle period of the Proterozoic Eon in a period called Calymmian. The title of the period comes from the Greek word for "cover".

The first period of the Mesoproterozoic Era only lasted 200 million years (1600 to 1400 million years ago) but with a brief summary, a lot started to happen - the continuing expansion of land platforms from the original cratons; photosynthetic organisms began to become more diverse; the free oxygen content increased in the atmosphere; a formation of ozone started to create a layer (it eventually settles in the stratosphere and it was thought that eukaryotic nucleated cells appeared at around the same time as the breakup of the supercontinent Columbia (around 1,500 million years ago).

It could be said that the formation of the ozone layer is one of the more important features of the Calymmian Period (although as I am beginning to figure out everything has its place and its importance). The current position of the stratosphere is situated between about 10 kilometres (6 miles in old money - nearly the distance from Whatlington to Hastings on the A21) and 50 kilometres (30 miles - nearly the distance from Whatlington to Sevenoaks in Kent) above the planet's surface at moderate latitudes. But like with all life there is an exception, at both the north and south, it starts at about 8 kilometres (5 miles - the approximate distance between Whatlington and the far side of Battle) above the surface.

Three oxygen atoms combine to form tropospheric and stratospheric ozone or O3; for this blog posting we are more interested in the stratospheric ozone  that plays absorbs a large percentage of the UV-B rays. Weirdly, it still allows a proportion of the damaging UV-B rays through that heats the stratosphere to around a current temperature of minus 3 degrees centigrade or 29.6 degrees Fahrenheit and heats the planet's surface. As an article by NOAA (National Oceanic and Atmospheric  Administration) states: "Ozone thus plays a key role in the temperature structure of the Earth's atmosphere". Without the reduction of the UV-B rays, both animals and plants would be damaged  as proved through experimentation. 

Next Time: The Ectasian Period